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	$117.31	11.862%	$131.2253	$131.23	$131.25	$131.20
Purchase #2	$218.93	11.347%	$243.772	$243.77	$243.75	$243.80
Purchase #3	$32.72	3.210%	$33.7703	$33.77	$33.75	$33.80
Purchase #4	$32.41	10.697%	$35.8769	$35.88	$35.90	$35.90
Purchase #5	$209.42	9.771%	$229.8824	$229.88	$229.90	$229.90
Purchase #6	$56.40	11.139%	$62.6824	$62.68	$62.70	$62.70
Purchase #7	$248.78	9.753%	$273.0435	$273.04	$273.05	$273.00
7 purchase totals =	$915.97		$1,010.2528	$1,010.25	$1,010.30	$1,010.30