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	$53.74	10.768%	$59.5267	$59.53	$59.55	$59.50
Purchase #2	$223.87	13.721%	$254.5872	$254.59	$254.60	$254.60
Purchase #3	$106.77	6.196%	$113.3855	$113.39	$113.40	$113.40
Purchase #4	$214.72	13.760%	$244.2655	$244.27	$244.25	$244.30
Purchase #5	$25.36	12.179%	$28.4486	$28.45	$28.45	$28.40
Purchase #6	$74.93	8.319%	$81.1634	$81.16	$81.15	$81.20
Purchase #7	$128.25	10.677%	$141.9433	$141.94	$141.95	$141.90
7 purchase totals =	$827.64		$923.3202	$923.33	$923.35	$923.30