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	$210.68	7.633%	$226.7612	$226.76	$226.75	$226.80
Purchase #2	$41.49	9.394%	$45.3876	$45.39	$45.40	$45.40
Purchase #3	$70.27	8.473%	$76.224	$76.22	$76.20	$76.20
Purchase #4	$167.91	12.848%	$189.4831	$189.48	$189.50	$189.50
Purchase #5	$158.48	10.367%	$174.9096	$174.91	$174.90	$174.90
Purchase #6	$198.78	12.334%	$223.2975	$223.30	$223.30	$223.30
Purchase #7	$242.59	7.488%	$260.7551	$260.76	$260.75	$260.80
7 purchase totals =	$1,090.20		$1,196.8181	$1,196.82	$1,196.80	$1,196.90