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	$173.26	12.227%	$194.4445	$194.44	$194.45	$194.40
Purchase #2	$165.31	8.367%	$179.1415	$179.14	$179.15	$179.10
Purchase #3	$76.70	4.808%	$80.3877	$80.39	$80.40	$80.40
Purchase #4	$33.29	6.443%	$35.4349	$35.43	$35.45	$35.40
Purchase #5	$39.95	6.668%	$42.6139	$42.61	$42.60	$42.60
Purchase #6	$134.70	7.323%	$144.5641	$144.56	$144.55	$144.60
Purchase #7	$92.26	7.646%	$99.3142	$99.31	$99.30	$99.30
7 purchase totals =	$715.47		$775.9008	$775.88	$775.90	$775.80