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	$193.66	8.839%	$210.7776	$210.78	$210.80	$210.80
Purchase #2	$188.88	12.706%	$212.8791	$212.88	$212.90	$212.90
Purchase #3	$59.78	5.285%	$62.9394	$62.94	$62.95	$62.90
Purchase #4	$82.77	12.171%	$92.8439	$92.84	$92.85	$92.80
Purchase #5	$39.45	11.584%	$44.0199	$44.02	$44.00	$44.00
Purchase #6	$79.30	13.316%	$89.8596	$89.86	$89.85	$89.90
Purchase #7	$177.61	3.199%	$183.2917	$183.29	$183.30	$183.30
7 purchase totals =	$821.45		$896.6112	$896.61	$896.65	$896.60