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	$157.57	9.157%	$171.9987	$172.00	$172.00	$172.00
Purchase #2	$233.59	3.839%	$242.5575	$242.56	$242.55	$242.60
Purchase #3	$238.39	9.369%	$260.7248	$260.72	$260.70	$260.70
Purchase #4	$179.84	13.148%	$203.4854	$203.49	$203.50	$203.50
Purchase #5	$91.42	13.598%	$103.8513	$103.85	$103.85	$103.90
Purchase #6	$79.59	11.850%	$89.0214	$89.02	$89.00	$89.00
Purchase #7	$28.92	13.533%	$32.8337	$32.83	$32.85	$32.80
7 purchase totals =	$1,009.32		$1,104.4728	$1,104.47	$1,104.45	$1,104.50