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	$36.63	3.642%	$37.9641	$37.96	$37.95	$38.00
Purchase #2	$151.73	12.806%	$171.1605	$171.16	$171.15	$171.20
Purchase #3	$154.51	10.320%	$170.4554	$170.46	$170.45	$170.50
Purchase #4	$249.53	5.858%	$264.1475	$264.15	$264.15	$264.10
Purchase #5	$86.29	3.198%	$89.0496	$89.05	$89.05	$89.00
Purchase #6	$171.98	6.417%	$183.016	$183.02	$183.00	$183.00
Purchase #7	$247.63	13.340%	$280.6638	$280.66	$280.65	$280.70
7 purchase totals =	$1,098.30		$1,196.4569	$1,196.46	$1,196.40	$1,196.50