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	$98.37	5.271%	$103.5551	$103.56	$103.55	$103.60
Purchase #2	$136.56	6.514%	$145.4555	$145.46	$145.45	$145.50
Purchase #3	$111.27	13.774%	$126.5963	$126.60	$126.60	$126.60
Purchase #4	$244.39	3.792%	$253.6573	$253.66	$253.65	$253.70
Purchase #5	$165.58	11.409%	$184.471	$184.47	$184.45	$184.50
Purchase #6	$225.79	11.496%	$251.7468	$251.75	$251.75	$251.70
Purchase #7	$189.63	3.574%	$196.4074	$196.41	$196.40	$196.40
7 purchase totals =	$1,171.59		$1,261.8894	$1,261.91	$1,261.85	$1,262.00