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	$132.95	5.415%	$140.1492	$140.15	$140.15	$140.10
Purchase #2	$58.84	11.424%	$65.5619	$65.56	$65.55	$65.60
Purchase #3	$89.65	13.235%	$101.5152	$101.52	$101.50	$101.50
Purchase #4	$127.85	3.130%	$131.8517	$131.85	$131.85	$131.90
Purchase #5	$15.97	5.164%	$16.7947	$16.79	$16.80	$16.80
Purchase #6	$124.51	5.688%	$131.5921	$131.59	$131.60	$131.60
Purchase #7	$70.55	10.489%	$77.95	$77.95	$77.95	$78.00
7 purchase totals =	$620.32		$665.4148	$665.41	$665.40	$665.50