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	$85.51	5.680%	$90.367	$90.37	$90.35	$90.40
Purchase #2	$181.76	4.123%	$189.254	$189.25	$189.25	$189.30
Purchase #3	$58.60	7.180%	$62.8075	$62.81	$62.80	$62.80
Purchase #4	$214.29	13.301%	$242.7927	$242.79	$242.80	$242.80
Purchase #5	$147.57	3.734%	$153.0803	$153.08	$153.10	$153.10
Purchase #6	$33.41	12.194%	$37.484	$37.48	$37.50	$37.50
Purchase #7	$210.58	3.221%	$217.3628	$217.36	$217.35	$217.40
7 purchase totals =	$931.72		$993.1483	$993.14	$993.15	$993.30