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	$236.59	5.280%	$249.082	$249.08	$249.10	$249.10
Purchase #2	$246.48	3.632%	$255.4322	$255.43	$255.45	$255.40
Purchase #3	$93.44	10.400%	$103.1578	$103.16	$103.15	$103.20
Purchase #4	$156.34	3.708%	$162.1371	$162.14	$162.15	$162.10
Purchase #5	$165.54	4.578%	$173.1184	$173.12	$173.10	$173.10
Purchase #6	$16.89	10.630%	$18.6854	$18.69	$18.70	$18.70
Purchase #7	$57.43	5.322%	$60.4864	$60.49	$60.50	$60.50
7 purchase totals =	$972.71		$1,022.0993	$1,022.11	$1,022.15	$1,022.10