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	$67.89	5.739%	$71.7862	$71.79	$71.80	$71.80
Purchase #2	$58.54	8.845%	$63.7179	$63.72	$63.70	$63.70
Purchase #3	$245.93	9.631%	$269.6155	$269.62	$269.60	$269.60
Purchase #4	$156.73	3.607%	$162.3833	$162.38	$162.40	$162.40
Purchase #5	$32.90	10.198%	$36.2551	$36.26	$36.25	$36.30
Purchase #6	$33.79	10.219%	$37.243	$37.24	$37.25	$37.20
Purchase #7	$130.93	11.799%	$146.3784	$146.38	$146.40	$146.40
7 purchase totals =	$726.71		$787.3794	$787.39	$787.40	$787.40