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	$20.64	10.227%	$22.7509	$22.75	$22.75	$22.80
Purchase #2	$59.79	13.572%	$67.9047	$67.90	$67.90	$67.90
Purchase #3	$93.37	9.137%	$101.9012	$101.90	$101.90	$101.90
Purchase #4	$115.94	6.305%	$123.25	$123.25	$123.25	$123.30
Purchase #5	$215.74	5.731%	$228.1041	$228.10	$228.10	$228.10
Purchase #6	$56.33	10.345%	$62.1573	$62.16	$62.15	$62.20
Purchase #7	$54.37	9.756%	$59.6743	$59.67	$59.65	$59.70
7 purchase totals =	$616.18		$665.7425	$665.73	$665.70	$665.90