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	$104.77	6.335%	$111.4072	$111.41	$111.40	$111.40
Purchase #2	$95.97	5.376%	$101.1293	$101.13	$101.15	$101.10
Purchase #3	$111.83	7.425%	$120.1334	$120.13	$120.15	$120.10
Purchase #4	$98.66	12.677%	$111.1671	$111.17	$111.15	$111.20
Purchase #5	$150.54	12.488%	$169.3394	$169.34	$169.35	$169.30
Purchase #6	$175.63	10.694%	$194.4119	$194.41	$194.40	$194.40
Purchase #7	$141.57	11.108%	$157.2956	$157.30	$157.30	$157.30
7 purchase totals =	$878.97		$964.8839	$964.89	$964.90	$964.80