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	$42.85	6.346%	$45.5693	$45.57	$45.55	$45.60
Purchase #2	$122.30	6.533%	$130.2899	$130.29	$130.30	$130.30
Purchase #3	$179.96	11.199%	$200.1137	$200.11	$200.10	$200.10
Purchase #4	$242.98	3.647%	$251.8415	$251.84	$251.85	$251.80
Purchase #5	$64.37	11.710%	$71.9077	$71.91	$71.90	$71.90
Purchase #6	$140.94	3.440%	$145.7883	$145.79	$145.80	$145.80
Purchase #7	$232.27	10.562%	$256.8024	$256.80	$256.80	$256.80
7 purchase totals =	$1,025.67		$1,102.3128	$1,102.31	$1,102.30	$1,102.30