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	$97.77	13.873%	$111.3336	$111.33	$111.35	$111.30
Purchase #2	$117.80	11.860%	$131.7711	$131.77	$131.75	$131.80
Purchase #3	$57.48	10.761%	$63.6654	$63.67	$63.65	$63.70
Purchase #4	$133.36	13.731%	$151.6717	$151.67	$151.65	$151.70
Purchase #5	$154.97	9.735%	$170.0563	$170.06	$170.05	$170.10
Purchase #6	$232.99	7.553%	$250.5877	$250.59	$250.60	$250.60
Purchase #7	$77.91	7.256%	$83.5631	$83.56	$83.55	$83.60
7 purchase totals =	$872.28		$962.6489	$962.65	$962.60	$962.80