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	$200.46	9.104%	$218.7099	$218.71	$218.70	$218.70
Purchase #2	$167.62	5.136%	$176.229	$176.23	$176.25	$176.20
Purchase #3	$213.86	11.685%	$238.8495	$238.85	$238.85	$238.80
Purchase #4	$173.38	5.394%	$182.7321	$182.73	$182.75	$182.70
Purchase #5	$102.77	8.406%	$111.4088	$111.41	$111.40	$111.40
Purchase #6	$85.79	7.170%	$91.9411	$91.94	$91.95	$91.90
Purchase #7	$128.55	10.749%	$142.3678	$142.37	$142.35	$142.40
7 purchase totals =	$1,072.43		$1,162.2382	$1,162.24	$1,162.25	$1,162.10