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	$189.86	11.802%	$212.2673	$212.27	$212.25	$212.30
Purchase #2	$189.74	7.369%	$203.7219	$203.72	$203.70	$203.70
Purchase #3	$142.49	6.303%	$151.4711	$151.47	$151.45	$151.50
Purchase #4	$176.66	8.859%	$192.3103	$192.31	$192.30	$192.30
Purchase #5	$172.67	13.780%	$196.4639	$196.46	$196.45	$196.50
Purchase #6	$39.31	10.190%	$43.3157	$43.32	$43.30	$43.30
Purchase #7	$154.75	5.210%	$162.8125	$162.81	$162.80	$162.80
7 purchase totals =	$1,065.48		$1,162.3627	$1,162.36	$1,162.25	$1,162.40