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	$20.57	8.388%	$22.2954	$22.30	$22.30	$22.30
Purchase #2	$45.82	6.518%	$48.8065	$48.81	$48.80	$48.80
Purchase #3	$63.32	13.568%	$71.9113	$71.91	$71.90	$71.90
Purchase #4	$162.65	6.139%	$172.6351	$172.64	$172.65	$172.60
Purchase #5	$62.37	3.496%	$64.5505	$64.55	$64.55	$64.60
Purchase #6	$114.41	7.601%	$123.1063	$123.11	$123.10	$123.10
Purchase #7	$204.36	12.405%	$229.7109	$229.71	$229.70	$229.70
7 purchase totals =	$673.50		$733.0160	$733.03	$733.00	$733.00