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	$147.55	5.502%	$155.6682	$155.67	$155.65	$155.70
Purchase #2	$95.28	5.848%	$100.852	$100.85	$100.85	$100.90
Purchase #3	$77.46	11.219%	$86.1502	$86.15	$86.15	$86.20
Purchase #4	$62.89	5.474%	$66.3326	$66.33	$66.35	$66.30
Purchase #5	$141.81	3.148%	$146.2742	$146.27	$146.25	$146.30
Purchase #6	$174.47	5.320%	$183.7518	$183.75	$183.75	$183.80
Purchase #7	$78.70	3.373%	$81.3546	$81.35	$81.35	$81.40
7 purchase totals =	$778.16		$820.3836	$820.37	$820.35	$820.60