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	$152.33	13.785%	$173.3287	$173.33	$173.35	$173.30
Purchase #2	$124.84	10.428%	$137.8583	$137.86	$137.85	$137.90
Purchase #3	$231.28	10.230%	$254.9399	$254.94	$254.95	$254.90
Purchase #4	$239.47	10.368%	$264.2982	$264.30	$264.30	$264.30
Purchase #5	$123.69	6.390%	$131.5938	$131.59	$131.60	$131.60
Purchase #6	$248.44	6.499%	$264.5861	$264.59	$264.60	$264.60
Purchase #7	$9.88	7.559%	$10.6268	$10.63	$10.65	$10.60
7 purchase totals =	$1,129.93		$1,237.2318	$1,237.24	$1,237.30	$1,237.20