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	$146.69	4.613%	$153.4568	$153.46	$153.45	$153.50
Purchase #2	$165.64	9.171%	$180.8308	$180.83	$180.85	$180.80
Purchase #3	$115.96	11.727%	$129.5586	$129.56	$129.55	$129.60
Purchase #4	$193.58	7.706%	$208.4973	$208.50	$208.50	$208.50
Purchase #5	$22.52	9.552%	$24.6711	$24.67	$24.65	$24.70
Purchase #6	$248.90	12.817%	$280.8015	$280.80	$280.80	$280.80
Purchase #7	$49.54	5.645%	$52.3365	$52.34	$52.35	$52.30
7 purchase totals =	$942.83		$1,030.1526	$1,030.16	$1,030.15	$1,030.20