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	$220.28	8.360%	$238.6954	$238.70	$238.70	$238.70
Purchase #2	$90.37	13.858%	$102.8935	$102.89	$102.90	$102.90
Purchase #3	$67.76	3.718%	$70.2793	$70.28	$70.30	$70.30
Purchase #4	$156.30	10.514%	$172.7334	$172.73	$172.75	$172.70
Purchase #5	$219.64	4.681%	$229.9213	$229.92	$229.90	$229.90
Purchase #6	$45.90	5.527%	$48.4369	$48.44	$48.45	$48.40
Purchase #7	$240.84	5.643%	$254.4306	$254.43	$254.45	$254.40
7 purchase totals =	$1,041.09		$1,117.3904	$1,117.39	$1,117.45	$1,117.30