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	$221.46	10.652%	$245.0499	$245.05	$245.05	$245.00
Purchase #2	$56.74	10.694%	$62.8078	$62.81	$62.80	$62.80
Purchase #3	$23.67	7.542%	$25.4552	$25.46	$25.45	$25.50
Purchase #4	$55.48	5.471%	$58.5153	$58.52	$58.50	$58.50
Purchase #5	$195.57	7.664%	$210.5585	$210.56	$210.55	$210.60
Purchase #6	$82.42	8.566%	$89.4801	$89.48	$89.50	$89.50
Purchase #7	$98.44	11.240%	$109.5047	$109.50	$109.50	$109.50
7 purchase totals =	$733.78		$801.3715	$801.38	$801.35	$801.40