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	$57.57	4.777%	$60.3201	$60.32	$60.30	$60.30
Purchase #2	$10.71	13.452%	$12.1507	$12.15	$12.15	$12.20
Purchase #3	$39.31	10.385%	$43.3923	$43.39	$43.40	$43.40
Purchase #4	$141.98	5.857%	$150.2958	$150.30	$150.30	$150.30
Purchase #5	$114.68	13.138%	$129.7467	$129.75	$129.75	$129.70
Purchase #6	$195.45	13.471%	$221.7791	$221.78	$221.80	$221.80
Purchase #7	$52.82	13.141%	$59.7611	$59.76	$59.75	$59.80
7 purchase totals =	$612.52		$677.4458	$677.45	$677.45	$677.50