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	$62.54	6.199%	$66.4169	$66.42	$66.40	$66.40
Purchase #2	$7.40	5.500%	$7.807	$7.81	$7.80	$7.80
Purchase #3	$52.89	10.555%	$58.4725	$58.47	$58.45	$58.50
Purchase #4	$29.42	13.203%	$33.3043	$33.30	$33.30	$33.30
Purchase #5	$223.69	8.525%	$242.7596	$242.76	$242.75	$242.80
Purchase #6	$186.40	12.764%	$210.1921	$210.19	$210.20	$210.20
Purchase #7	$185.90	3.216%	$191.8785	$191.88	$191.90	$191.90
7 purchase totals =	$748.24		$810.8309	$810.83	$810.80	$810.90