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	$120.30	8.201%	$130.1658	$130.17	$130.15	$130.20
Purchase #2	$148.25	8.119%	$160.2864	$160.29	$160.30	$160.30
Purchase #3	$189.67	4.398%	$198.0117	$198.01	$198.00	$198.00
Purchase #4	$169.69	11.170%	$188.6444	$188.64	$188.65	$188.60
Purchase #5	$110.33	11.578%	$123.104	$123.10	$123.10	$123.10
Purchase #6	$214.63	13.614%	$243.8497	$243.85	$243.85	$243.80
Purchase #7	$152.82	5.620%	$161.4085	$161.41	$161.40	$161.40
7 purchase totals =	$1,105.69		$1,205.4705	$1,205.47	$1,205.45	$1,205.40