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	$196.73	12.612%	$221.5416	$221.54	$221.55	$221.50
Purchase #2	$27.81	13.664%	$31.61	$31.61	$31.60	$31.60
Purchase #3	$101.31	10.161%	$111.6041	$111.60	$111.60	$111.60
Purchase #4	$109.41	10.726%	$121.1453	$121.15	$121.15	$121.10
Purchase #5	$135.74	10.862%	$150.4841	$150.48	$150.50	$150.50
Purchase #6	$182.31	12.675%	$205.4178	$205.42	$205.40	$205.40
Purchase #7	$120.69	11.644%	$134.7431	$134.74	$134.75	$134.70
7 purchase totals =	$874.00		$976.5460	$976.54	$976.55	$976.40