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	$40.90	10.828%	$45.3287	$45.33	$45.35	$45.30
Purchase #2	$171.58	10.823%	$190.1501	$190.15	$190.15	$190.20
Purchase #3	$54.79	4.664%	$57.3454	$57.35	$57.35	$57.30
Purchase #4	$106.29	11.391%	$118.3975	$118.40	$118.40	$118.40
Purchase #5	$79.25	4.185%	$82.5666	$82.57	$82.55	$82.60
Purchase #6	$171.27	5.320%	$180.3816	$180.38	$180.40	$180.40
Purchase #7	$86.97	11.218%	$96.7263	$96.73	$96.75	$96.70
7 purchase totals =	$711.05		$770.8962	$770.91	$770.95	$770.90