Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$134.99	11.220%	$150.1359	$150.14	$150.15	$150.10
Purchase #2	$210.78	10.708%	$233.3503	$233.35	$233.35	$233.40
Purchase #3	$138.31	5.453%	$145.852	$145.85	$145.85	$145.90
Purchase #4	$163.31	5.247%	$171.8789	$171.88	$171.90	$171.90
Purchase #5	$95.94	4.524%	$100.2803	$100.28	$100.30	$100.30
Purchase #6	$120.99	13.804%	$137.6915	$137.69	$137.70	$137.70
Purchase #7	$158.79	13.710%	$180.5601	$180.56	$180.55	$180.60
7 purchase totals =	$1,023.11		$1,119.7490	$1,119.75	$1,119.80	$1,119.90