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	$47.82	10.173%	$52.6847	$52.68	$52.70	$52.70
Purchase #2	$237.65	3.743%	$246.5452	$246.55	$246.55	$246.50
Purchase #3	$128.90	3.102%	$132.8985	$132.90	$132.90	$132.90
Purchase #4	$220.72	3.371%	$228.1605	$228.16	$228.15	$228.20
Purchase #5	$120.31	13.166%	$136.15	$136.15	$136.15	$136.20
Purchase #6	$90.70	6.768%	$96.8386	$96.84	$96.85	$96.80
Purchase #7	$216.40	3.155%	$223.2274	$223.23	$223.25	$223.20
7 purchase totals =	$1,062.50		$1,116.5049	$1,116.51	$1,116.55	$1,116.50