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	$234.59	8.530%	$254.6005	$254.60	$254.60	$254.60
Purchase #2	$85.61	6.778%	$91.4126	$91.41	$91.40	$91.40
Purchase #3	$73.89	3.508%	$76.4821	$76.48	$76.50	$76.50
Purchase #4	$206.90	5.662%	$218.6147	$218.61	$218.60	$218.60
Purchase #5	$240.75	6.479%	$256.3482	$256.35	$256.35	$256.30
Purchase #6	$148.55	5.381%	$156.5435	$156.54	$156.55	$156.50
Purchase #7	$96.59	5.521%	$101.9227	$101.92	$101.90	$101.90
7 purchase totals =	$1,086.88		$1,155.9243	$1,155.91	$1,155.90	$1,155.80