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	$58.68	3.113%	$60.5067	$60.51	$60.50	$60.50
Purchase #2	$76.63	6.424%	$81.5527	$81.55	$81.55	$81.60
Purchase #3	$242.86	12.704%	$273.7129	$273.71	$273.70	$273.70
Purchase #4	$158.43	3.198%	$163.4966	$163.50	$163.50	$163.50
Purchase #5	$199.90	11.651%	$223.1903	$223.19	$223.20	$223.20
Purchase #6	$189.56	3.802%	$196.7671	$196.77	$196.75	$196.80
Purchase #7	$105.27	7.604%	$113.2747	$113.27	$113.25	$113.30
7 purchase totals =	$1,031.33		$1,112.5010	$1,112.50	$1,112.45	$1,112.60