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	$55.90	11.478%	$62.3162	$62.32	$62.30	$62.30
Purchase #2	$244.28	12.590%	$275.0349	$275.03	$275.05	$275.00
Purchase #3	$41.81	8.488%	$45.3588	$45.36	$45.35	$45.40
Purchase #4	$17.77	4.391%	$18.5503	$18.55	$18.55	$18.60
Purchase #5	$97.60	3.116%	$100.6412	$100.64	$100.65	$100.60
Purchase #6	$89.26	11.797%	$99.79	$99.79	$99.80	$99.80
Purchase #7	$232.86	13.346%	$263.9375	$263.94	$263.95	$263.90
7 purchase totals =	$779.48		$865.6289	$865.63	$865.65	$865.60