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	$89.58	13.737%	$101.8856	$101.89	$101.90	$101.90
Purchase #2	$214.31	5.414%	$225.9127	$225.91	$225.90	$225.90
Purchase #3	$208.52	10.542%	$230.5022	$230.50	$230.50	$230.50
Purchase #4	$155.82	7.636%	$167.7184	$167.72	$167.70	$167.70
Purchase #5	$83.73	13.279%	$94.8485	$94.85	$94.85	$94.80
Purchase #6	$246.69	4.806%	$258.5459	$258.55	$258.55	$258.50
Purchase #7	$92.41	13.538%	$104.9205	$104.92	$104.90	$104.90
7 purchase totals =	$1,091.06		$1,184.3338	$1,184.34	$1,184.30	$1,184.20