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	$125.90	6.707%	$134.3441	$134.34	$134.35	$134.30
Purchase #2	$138.58	9.170%	$151.2878	$151.29	$151.30	$151.30
Purchase #3	$142.38	13.445%	$161.523	$161.52	$161.50	$161.50
Purchase #4	$249.74	4.640%	$261.3279	$261.33	$261.35	$261.30
Purchase #5	$54.94	8.648%	$59.6912	$59.69	$59.70	$59.70
Purchase #6	$52.30	3.516%	$54.1389	$54.14	$54.15	$54.10
Purchase #7	$168.52	9.705%	$184.8749	$184.87	$184.85	$184.90
7 purchase totals =	$932.36		$1,007.1878	$1,007.18	$1,007.20	$1,007.10