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	$107.77	3.708%	$111.7661	$111.77	$111.75	$111.80
Purchase #2	$87.91	9.389%	$96.1639	$96.16	$96.15	$96.20
Purchase #3	$96.63	9.400%	$105.7132	$105.71	$105.70	$105.70
Purchase #4	$162.42	10.122%	$178.8602	$178.86	$178.85	$178.90
Purchase #5	$129.47	10.421%	$142.9621	$142.96	$142.95	$143.00
Purchase #6	$94.87	13.744%	$107.9089	$107.91	$107.90	$107.90
Purchase #7	$54.53	5.543%	$57.5526	$57.55	$57.55	$57.60
7 purchase totals =	$733.60		$800.9270	$800.92	$800.85	$801.10