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	$100.54	11.373%	$111.9744	$111.97	$111.95	$112.00
Purchase #2	$152.32	9.365%	$166.5848	$166.58	$166.60	$166.60
Purchase #3	$41.46	3.839%	$43.0516	$43.05	$43.05	$43.10
Purchase #4	$127.91	6.437%	$136.1436	$136.14	$136.15	$136.10
Purchase #5	$173.48	13.490%	$196.8825	$196.88	$196.90	$196.90
Purchase #6	$166.51	11.570%	$185.7752	$185.78	$185.80	$185.80
Purchase #7	$99.53	6.207%	$105.7078	$105.71	$105.70	$105.70
7 purchase totals =	$861.75		$946.1199	$946.11	$946.15	$946.20