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	$199.34	10.487%	$220.2448	$220.24	$220.25	$220.20
Purchase #2	$230.61	5.484%	$243.2567	$243.26	$243.25	$243.30
Purchase #3	$123.38	10.290%	$136.0758	$136.08	$136.10	$136.10
Purchase #4	$158.77	10.299%	$175.1217	$175.12	$175.10	$175.10
Purchase #5	$104.64	6.242%	$111.1716	$111.17	$111.15	$111.20
Purchase #6	$69.89	13.449%	$79.2895	$79.29	$79.30	$79.30
Purchase #7	$88.90	7.285%	$95.3764	$95.38	$95.40	$95.40
7 purchase totals =	$975.53		$1,060.5365	$1,060.54	$1,060.55	$1,060.60