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	$179.56	6.615%	$191.4379	$191.44	$191.45	$191.40
Purchase #2	$33.73	5.608%	$35.6216	$35.62	$35.60	$35.60
Purchase #3	$233.69	6.345%	$248.5176	$248.52	$248.50	$248.50
Purchase #4	$88.35	8.395%	$95.767	$95.77	$95.75	$95.80
Purchase #5	$175.69	3.317%	$181.5176	$181.52	$181.50	$181.50
Purchase #6	$181.52	9.194%	$198.2089	$198.21	$198.20	$198.20
Purchase #7	$187.31	6.850%	$200.1407	$200.14	$200.15	$200.10
7 purchase totals =	$1,079.85		$1,151.2113	$1,151.22	$1,151.15	$1,151.10