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	$17.51	4.231%	$18.2508	$18.25	$18.25	$18.30
Purchase #2	$155.56	11.440%	$173.3561	$173.36	$173.35	$173.40
Purchase #3	$64.69	10.434%	$71.4398	$71.44	$71.45	$71.40
Purchase #4	$221.76	5.353%	$233.6308	$233.63	$233.65	$233.60
Purchase #5	$235.42	13.796%	$267.8985	$267.90	$267.90	$267.90
Purchase #6	$79.35	12.841%	$89.5393	$89.54	$89.55	$89.50
Purchase #7	$169.44	6.675%	$180.7501	$180.75	$180.75	$180.80
7 purchase totals =	$943.73		$1,034.8654	$1,034.87	$1,034.90	$1,034.90