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	$32.92	13.608%	$37.3998	$37.40	$37.40	$37.40
Purchase #2	$7.66	11.265%	$8.5229	$8.52	$8.50	$8.50
Purchase #3	$67.76	6.375%	$72.0797	$72.08	$72.10	$72.10
Purchase #4	$31.78	3.213%	$32.8011	$32.80	$32.80	$32.80
Purchase #5	$184.77	13.570%	$209.8433	$209.84	$209.85	$209.80
Purchase #6	$99.57	5.785%	$105.3301	$105.33	$105.35	$105.30
Purchase #7	$14.27	3.676%	$14.7946	$14.79	$14.80	$14.80
7 purchase totals =	$438.73		$480.7715	$480.76	$480.80	$480.70