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	$197.93	11.823%	$221.3313	$221.33	$221.35	$221.30
Purchase #2	$185.58	13.192%	$210.0617	$210.06	$210.05	$210.10
Purchase #3	$115.59	10.494%	$127.72	$127.72	$127.70	$127.70
Purchase #4	$66.55	7.549%	$71.5739	$71.57	$71.55	$71.60
Purchase #5	$202.87	10.166%	$223.4938	$223.49	$223.50	$223.50
Purchase #6	$84.61	7.534%	$90.9845	$90.98	$91.00	$91.00
Purchase #7	$69.59	3.761%	$72.2073	$72.21	$72.20	$72.20
7 purchase totals =	$922.72		$1,017.3725	$1,017.36	$1,017.35	$1,017.40