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	$151.78	6.360%	$161.4332	$161.43	$161.45	$161.40
Purchase #2	$225.39	6.583%	$240.2274	$240.23	$240.25	$240.20
Purchase #3	$120.59	3.102%	$124.3307	$124.33	$124.35	$124.30
Purchase #4	$237.30	6.844%	$253.5408	$253.54	$253.55	$253.50
Purchase #5	$161.31	4.473%	$168.5254	$168.53	$168.55	$168.50
Purchase #6	$52.45	12.448%	$58.979	$58.98	$59.00	$59.00
Purchase #7	$155.61	6.723%	$166.0717	$166.07	$166.05	$166.10
7 purchase totals =	$1,104.43		$1,173.1082	$1,173.11	$1,173.20	$1,173.00