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	$225.46	10.332%	$248.7545	$248.75	$248.75	$248.80
Purchase #2	$180.28	6.761%	$192.4687	$192.47	$192.45	$192.50
Purchase #3	$6.94	3.839%	$7.2064	$7.21	$7.20	$7.20
Purchase #4	$182.45	7.785%	$196.6537	$196.65	$196.65	$196.70
Purchase #5	$52.45	3.170%	$54.1127	$54.11	$54.10	$54.10
Purchase #6	$73.31	13.816%	$83.4385	$83.44	$83.45	$83.40
Purchase #7	$250.34	9.163%	$273.2787	$273.28	$273.30	$273.30
7 purchase totals =	$971.23		$1,055.9132	$1,055.91	$1,055.90	$1,056.00