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	$128.27	11.231%	$142.676	$142.68	$142.70	$142.70
Purchase #2	$159.59	7.266%	$171.1858	$171.19	$171.20	$171.20
Purchase #3	$142.66	6.651%	$152.1483	$152.15	$152.15	$152.10
Purchase #4	$215.49	6.477%	$229.4473	$229.45	$229.45	$229.40
Purchase #5	$192.94	8.728%	$209.7798	$209.78	$209.80	$209.80
Purchase #6	$225.43	7.776%	$242.9594	$242.96	$242.95	$243.00
Purchase #7	$79.73	6.675%	$85.052	$85.05	$85.05	$85.10
7 purchase totals =	$1,144.11		$1,233.2486	$1,233.26	$1,233.30	$1,233.30