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	$238.31	12.331%	$267.696	$267.70	$267.70	$267.70
Purchase #2	$144.57	4.446%	$150.9976	$151.00	$151.00	$151.00
Purchase #3	$21.52	6.480%	$22.9145	$22.91	$22.90	$22.90
Purchase #4	$101.67	12.873%	$114.758	$114.76	$114.75	$114.80
Purchase #5	$124.93	11.467%	$139.2557	$139.26	$139.25	$139.30
Purchase #6	$104.60	4.851%	$109.6741	$109.67	$109.65	$109.70
Purchase #7	$98.25	13.617%	$111.6287	$111.63	$111.65	$111.60
7 purchase totals =	$833.85		$916.9246	$916.93	$916.90	$917.00