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	$196.69	6.267%	$209.0166	$209.02	$209.00	$209.00
Purchase #2	$113.48	4.585%	$118.6831	$118.68	$118.70	$118.70
Purchase #3	$189.89	10.828%	$210.4513	$210.45	$210.45	$210.50
Purchase #4	$173.72	7.258%	$186.3286	$186.33	$186.35	$186.30
Purchase #5	$106.95	4.476%	$111.7371	$111.74	$111.75	$111.70
Purchase #6	$231.75	5.645%	$244.8323	$244.83	$244.85	$244.80
Purchase #7	$18.98	5.526%	$20.0288	$20.03	$20.05	$20.00
7 purchase totals =	$1,031.46		$1,101.0778	$1,101.08	$1,101.15	$1,101.00