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	$115.72	9.767%	$127.0224	$127.02	$127.00	$127.00
Purchase #2	$79.76	5.782%	$84.3717	$84.37	$84.35	$84.40
Purchase #3	$244.91	7.334%	$262.8717	$262.87	$262.85	$262.90
Purchase #4	$160.99	6.843%	$172.0065	$172.01	$172.00	$172.00
Purchase #5	$82.85	8.107%	$89.5666	$89.57	$89.55	$89.60
Purchase #6	$182.37	8.293%	$197.4939	$197.49	$197.50	$197.50
Purchase #7	$141.86	13.819%	$161.4636	$161.46	$161.45	$161.50
7 purchase totals =	$1,008.46		$1,094.7964	$1,094.79	$1,094.70	$1,094.90