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	$98.51	7.152%	$105.5554	$105.56	$105.55	$105.60
Purchase #2	$130.73	11.276%	$145.4711	$145.47	$145.45	$145.50
Purchase #3	$235.34	5.862%	$249.1356	$249.14	$249.15	$249.10
Purchase #4	$178.46	5.201%	$187.7417	$187.74	$187.75	$187.70
Purchase #5	$160.60	11.787%	$179.5299	$179.53	$179.55	$179.50
Purchase #6	$194.76	8.111%	$210.557	$210.56	$210.55	$210.60
Purchase #7	$193.77	10.177%	$213.49	$213.49	$213.50	$213.50
7 purchase totals =	$1,192.17		$1,291.4807	$1,291.49	$1,291.50	$1,291.50