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	$148.54	13.477%	$168.5587	$168.56	$168.55	$168.60
Purchase #2	$250.67	10.117%	$276.0303	$276.03	$276.05	$276.00
Purchase #3	$34.73	10.660%	$38.4322	$38.43	$38.45	$38.40
Purchase #4	$175.67	7.326%	$188.5396	$188.54	$188.55	$188.50
Purchase #5	$212.57	10.228%	$234.3117	$234.31	$234.30	$234.30
Purchase #6	$167.36	10.823%	$185.4734	$185.47	$185.45	$185.50
Purchase #7	$56.92	13.786%	$64.767	$64.77	$64.75	$64.80
7 purchase totals =	$1,046.46		$1,156.1129	$1,156.11	$1,156.10	$1,156.10