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	$102.76	9.293%	$112.3095	$112.31	$112.30	$112.30
Purchase #2	$6.69	13.174%	$7.5713	$7.57	$7.55	$7.60
Purchase #3	$235.47	7.195%	$252.4121	$252.41	$252.40	$252.40
Purchase #4	$200.86	5.689%	$212.2869	$212.29	$212.30	$212.30
Purchase #5	$107.58	6.419%	$114.4856	$114.49	$114.50	$114.50
Purchase #6	$29.91	4.148%	$31.1507	$31.15	$31.15	$31.20
Purchase #7	$99.67	4.516%	$104.1711	$104.17	$104.15	$104.20
7 purchase totals =	$782.94		$834.3872	$834.39	$834.35	$834.50