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	$223.52	4.223%	$232.9592	$232.96	$232.95	$233.00
Purchase #2	$201.42	9.701%	$220.9598	$220.96	$220.95	$221.00
Purchase #3	$155.59	7.667%	$167.5191	$167.52	$167.50	$167.50
Purchase #4	$179.59	3.111%	$185.177	$185.18	$185.20	$185.20
Purchase #5	$62.57	8.275%	$67.7477	$67.75	$67.75	$67.70
Purchase #6	$99.55	11.846%	$111.3427	$111.34	$111.35	$111.30
Purchase #7	$210.55	6.282%	$223.7768	$223.78	$223.80	$223.80
7 purchase totals =	$1,132.79		$1,209.4823	$1,209.49	$1,209.50	$1,209.50