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	$174.40	6.274%	$185.3419	$185.34	$185.35	$185.30
Purchase #2	$245.32	10.673%	$271.503	$271.50	$271.50	$271.50
Purchase #3	$84.96	5.455%	$89.5946	$89.59	$89.60	$89.60
Purchase #4	$172.53	13.396%	$195.6421	$195.64	$195.65	$195.60
Purchase #5	$26.82	4.385%	$27.9961	$28.00	$28.00	$28.00
Purchase #6	$206.48	10.812%	$228.8046	$228.80	$228.80	$228.80
Purchase #7	$225.25	13.254%	$255.1046	$255.10	$255.10	$255.10
7 purchase totals =	$1,135.76		$1,253.9869	$1,253.97	$1,254.00	$1,253.90