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	$43.90	10.746%	$48.6175	$48.62	$48.60	$48.60
Purchase #2	$156.62	11.413%	$174.495	$174.50	$174.50	$174.50
Purchase #3	$46.57	4.431%	$48.6335	$48.63	$48.65	$48.60
Purchase #4	$78.56	5.146%	$82.6027	$82.60	$82.60	$82.60
Purchase #5	$96.78	13.771%	$110.1076	$110.11	$110.10	$110.10
Purchase #6	$241.82	11.287%	$269.1142	$269.11	$269.10	$269.10
Purchase #7	$27.79	3.196%	$28.6782	$28.68	$28.70	$28.70
7 purchase totals =	$692.04		$762.2487	$762.25	$762.25	$762.20