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	$157.50	11.731%	$175.9763	$175.98	$176.00	$176.00
Purchase #2	$178.56	10.181%	$196.7392	$196.74	$196.75	$196.70
Purchase #3	$112.89	13.247%	$127.8445	$127.84	$127.85	$127.80
Purchase #4	$185.73	12.523%	$208.989	$208.99	$209.00	$209.00
Purchase #5	$177.31	12.537%	$199.5394	$199.54	$199.55	$199.50
Purchase #6	$205.44	13.623%	$233.4271	$233.43	$233.45	$233.40
Purchase #7	$30.31	9.619%	$33.2255	$33.23	$33.25	$33.20
7 purchase totals =	$1,047.74		$1,175.7410	$1,175.75	$1,175.85	$1,175.60