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	$67.92	5.218%	$71.4641	$71.46	$71.45	$71.50
Purchase #2	$165.71	6.457%	$176.4099	$176.41	$176.40	$176.40
Purchase #3	$93.43	7.322%	$100.2709	$100.27	$100.25	$100.30
Purchase #4	$98.25	9.174%	$107.2635	$107.26	$107.25	$107.30
Purchase #5	$213.60	12.586%	$240.4837	$240.48	$240.50	$240.50
Purchase #6	$231.38	10.277%	$255.1589	$255.16	$255.15	$255.20
Purchase #7	$209.31	10.164%	$230.5843	$230.58	$230.60	$230.60
7 purchase totals =	$1,079.60		$1,181.6353	$1,181.62	$1,181.60	$1,181.80