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	$205.63	11.229%	$228.7202	$228.72	$228.70	$228.70
Purchase #2	$191.79	6.164%	$203.6119	$203.61	$203.60	$203.60
Purchase #3	$7.45	13.142%	$8.4291	$8.43	$8.45	$8.40
Purchase #4	$173.76	5.647%	$183.5722	$183.57	$183.55	$183.60
Purchase #5	$65.76	10.404%	$72.6017	$72.60	$72.60	$72.60
Purchase #6	$28.58	13.241%	$32.3643	$32.36	$32.35	$32.40
Purchase #7	$33.25	11.772%	$37.1642	$37.16	$37.15	$37.20
7 purchase totals =	$706.22		$766.4636	$766.45	$766.40	$766.50