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	$154.26	7.278%	$165.487	$165.49	$165.50	$165.50
Purchase #2	$135.36	6.760%	$144.5103	$144.51	$144.50	$144.50
Purchase #3	$26.64	6.714%	$28.4286	$28.43	$28.45	$28.40
Purchase #4	$231.61	13.761%	$263.4819	$263.48	$263.50	$263.50
Purchase #5	$237.67	11.177%	$264.2344	$264.23	$264.25	$264.20
Purchase #6	$128.79	10.486%	$142.2949	$142.29	$142.30	$142.30
Purchase #7	$120.31	11.622%	$134.2924	$134.29	$134.30	$134.30
7 purchase totals =	$1,034.64		$1,142.7295	$1,142.72	$1,142.80	$1,142.70