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	$221.83	9.603%	$243.1323	$243.13	$243.15	$243.10
Purchase #2	$97.60	6.521%	$103.9645	$103.96	$103.95	$104.00
Purchase #3	$211.77	3.787%	$219.7897	$219.79	$219.80	$219.80
Purchase #4	$56.88	4.381%	$59.3719	$59.37	$59.35	$59.40
Purchase #5	$110.49	11.553%	$123.2549	$123.25	$123.25	$123.30
Purchase #6	$243.56	10.758%	$269.7622	$269.76	$269.75	$269.80
Purchase #7	$73.85	4.337%	$77.0529	$77.05	$77.05	$77.10
7 purchase totals =	$1,015.98		$1,096.3284	$1,096.31	$1,096.30	$1,096.50