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	$110.97	13.569%	$126.0275	$126.03	$126.05	$126.00
Purchase #2	$241.46	11.791%	$269.9305	$269.93	$269.95	$269.90
Purchase #3	$158.58	4.359%	$165.4925	$165.49	$165.50	$165.50
Purchase #4	$92.51	8.434%	$100.3123	$100.31	$100.30	$100.30
Purchase #5	$160.67	10.755%	$177.9501	$177.95	$177.95	$178.00
Purchase #6	$87.62	3.581%	$90.7577	$90.76	$90.75	$90.80
Purchase #7	$87.74	3.608%	$90.9057	$90.91	$90.90	$90.90
7 purchase totals =	$939.55		$1,021.3763	$1,021.38	$1,021.40	$1,021.40