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	$50.62	3.486%	$52.3846	$52.38	$52.40	$52.40
Purchase #2	$199.40	5.404%	$210.1756	$210.18	$210.20	$210.20
Purchase #3	$93.28	5.723%	$98.6184	$98.62	$98.60	$98.60
Purchase #4	$142.45	6.662%	$151.94	$151.94	$151.95	$151.90
Purchase #5	$218.26	3.366%	$225.6066	$225.61	$225.60	$225.60
Purchase #6	$92.58	8.715%	$100.6483	$100.65	$100.65	$100.60
Purchase #7	$242.54	8.862%	$264.0339	$264.03	$264.05	$264.00
7 purchase totals =	$1,039.13		$1,103.4074	$1,103.41	$1,103.45	$1,103.30