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	$225.50	3.543%	$233.4895	$233.49	$233.50	$233.50
Purchase #2	$41.54	11.789%	$46.4372	$46.44	$46.45	$46.40
Purchase #3	$38.55	6.650%	$41.1136	$41.11	$41.10	$41.10
Purchase #4	$56.74	7.727%	$61.1243	$61.12	$61.10	$61.10
Purchase #5	$72.63	6.233%	$77.157	$77.16	$77.15	$77.20
Purchase #6	$111.38	4.470%	$116.3587	$116.36	$116.35	$116.40
Purchase #7	$222.32	5.490%	$234.5254	$234.53	$234.55	$234.50
7 purchase totals =	$768.66		$810.2057	$810.21	$810.20	$810.20