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	$244.78	12.482%	$275.3334	$275.33	$275.35	$275.30
Purchase #2	$10.51	8.497%	$11.403	$11.40	$11.40	$11.40
Purchase #3	$238.71	4.236%	$248.8218	$248.82	$248.80	$248.80
Purchase #4	$224.71	7.640%	$241.8778	$241.88	$241.90	$241.90
Purchase #5	$202.35	13.372%	$229.4082	$229.41	$229.40	$229.40
Purchase #6	$69.92	9.529%	$76.5827	$76.58	$76.60	$76.60
Purchase #7	$77.33	7.143%	$82.8537	$82.85	$82.85	$82.90
7 purchase totals =	$1,068.31		$1,166.2806	$1,166.27	$1,166.30	$1,166.30