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	$156.84	8.130%	$169.5911	$169.59	$169.60	$169.60
Purchase #2	$240.89	4.343%	$251.3519	$251.35	$251.35	$251.40
Purchase #3	$18.25	11.812%	$20.4057	$20.41	$20.40	$20.40
Purchase #4	$86.87	3.465%	$89.88	$89.88	$89.90	$89.90
Purchase #5	$61.32	6.295%	$65.1801	$65.18	$65.20	$65.20
Purchase #6	$40.94	7.124%	$43.8566	$43.86	$43.85	$43.90
Purchase #7	$210.35	7.171%	$225.4342	$225.43	$225.45	$225.40
7 purchase totals =	$815.46		$865.6996	$865.70	$865.75	$865.80