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	$178.25	12.294%	$200.1641	$200.16	$200.15	$200.20
Purchase #2	$202.27	3.502%	$209.3535	$209.35	$209.35	$209.40
Purchase #3	$157.76	7.813%	$170.0858	$170.09	$170.10	$170.10
Purchase #4	$196.33	10.734%	$217.4041	$217.40	$217.40	$217.40
Purchase #5	$235.26	11.123%	$261.428	$261.43	$261.45	$261.40
Purchase #6	$79.84	8.465%	$86.5985	$86.60	$86.60	$86.60
Purchase #7	$90.61	10.243%	$99.8912	$99.89	$99.90	$99.90
7 purchase totals =	$1,140.32		$1,244.9252	$1,244.92	$1,244.95	$1,245.00