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	$243.95	10.520%	$269.6135	$269.61	$269.60	$269.60
Purchase #2	$172.86	12.583%	$194.611	$194.61	$194.60	$194.60
Purchase #3	$216.54	7.846%	$233.5297	$233.53	$233.55	$233.50
Purchase #4	$137.77	4.199%	$143.555	$143.56	$143.55	$143.60
Purchase #5	$35.26	12.371%	$39.622	$39.62	$39.60	$39.60
Purchase #6	$96.27	7.590%	$103.5769	$103.58	$103.60	$103.60
Purchase #7	$60.54	6.233%	$64.3135	$64.31	$64.30	$64.30
7 purchase totals =	$963.19		$1,048.8216	$1,048.82	$1,048.80	$1,048.80