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	$248.66	8.328%	$269.3684	$269.37	$269.35	$269.40
Purchase #2	$88.53	7.131%	$94.8431	$94.84	$94.85	$94.80
Purchase #3	$124.57	5.790%	$131.7826	$131.78	$131.80	$131.80
Purchase #4	$156.32	7.290%	$167.7157	$167.72	$167.70	$167.70
Purchase #5	$174.80	12.499%	$196.6483	$196.65	$196.65	$196.60
Purchase #6	$96.72	13.721%	$109.991	$109.99	$110.00	$110.00
Purchase #7	$36.66	12.325%	$41.1783	$41.18	$41.20	$41.20
7 purchase totals =	$926.26		$1,011.5274	$1,011.53	$1,011.55	$1,011.50