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	$191.77	12.683%	$216.0922	$216.09	$216.10	$216.10
Purchase #2	$146.86	6.406%	$156.2679	$156.27	$156.25	$156.30
Purchase #3	$127.63	12.587%	$143.6948	$143.69	$143.70	$143.70
Purchase #4	$189.91	11.387%	$211.5351	$211.54	$211.55	$211.50
Purchase #5	$179.97	4.771%	$188.5564	$188.56	$188.55	$188.60
Purchase #6	$139.96	7.780%	$150.8489	$150.85	$150.85	$150.80
Purchase #7	$71.65	6.506%	$76.3115	$76.31	$76.30	$76.30
7 purchase totals =	$1,047.75		$1,143.3068	$1,143.31	$1,143.30	$1,143.30