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	$218.39	8.315%	$236.5491	$236.55	$236.55	$236.50
Purchase #2	$179.62	5.521%	$189.5368	$189.54	$189.55	$189.50
Purchase #3	$149.29	3.438%	$154.4226	$154.42	$154.40	$154.40
Purchase #4	$215.65	12.280%	$242.1318	$242.13	$242.15	$242.10
Purchase #5	$89.59	10.823%	$99.2863	$99.29	$99.30	$99.30
Purchase #6	$11.43	3.576%	$11.8387	$11.84	$11.85	$11.80
Purchase #7	$67.28	3.645%	$69.7324	$69.73	$69.75	$69.70
7 purchase totals =	$931.25		$1,003.4977	$1,003.50	$1,003.55	$1,003.30