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	$147.32	3.685%	$152.7487	$152.75	$152.75	$152.70
Purchase #2	$233.89	10.489%	$258.4227	$258.42	$258.40	$258.40
Purchase #3	$19.42	5.751%	$20.5368	$20.54	$20.55	$20.50
Purchase #4	$96.97	4.635%	$101.4646	$101.46	$101.45	$101.50
Purchase #5	$164.73	12.824%	$185.855	$185.86	$185.85	$185.90
Purchase #6	$158.53	6.450%	$168.7552	$168.76	$168.75	$168.80
Purchase #7	$55.89	5.857%	$59.1635	$59.16	$59.15	$59.20
7 purchase totals =	$876.75		$946.9465	$946.95	$946.90	$947.00