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	$224.83	12.596%	$253.1496	$253.15	$253.15	$253.10
Purchase #2	$201.58	10.514%	$222.7741	$222.77	$222.75	$222.80
Purchase #3	$182.83	6.826%	$195.31	$195.31	$195.30	$195.30
Purchase #4	$237.84	13.543%	$270.0507	$270.05	$270.05	$270.10
Purchase #5	$10.73	8.279%	$11.6183	$11.62	$11.60	$11.60
Purchase #6	$33.82	5.268%	$35.6016	$35.60	$35.60	$35.60
Purchase #7	$155.25	11.782%	$173.5416	$173.54	$173.55	$173.50
7 purchase totals =	$1,046.88		$1,162.0459	$1,162.04	$1,162.00	$1,162.00