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	$118.56	8.555%	$128.7028	$128.70	$128.70	$128.70
Purchase #2	$154.65	10.735%	$171.2517	$171.25	$171.25	$171.30
Purchase #3	$141.44	7.331%	$151.809	$151.81	$151.80	$151.80
Purchase #4	$69.69	4.223%	$72.633	$72.63	$72.65	$72.60
Purchase #5	$237.66	5.482%	$250.6885	$250.69	$250.70	$250.70
Purchase #6	$167.78	6.191%	$178.1673	$178.17	$178.15	$178.20
Purchase #7	$81.63	10.386%	$90.1081	$90.11	$90.10	$90.10
7 purchase totals =	$971.41		$1,043.3604	$1,043.36	$1,043.35	$1,043.40