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	$50.96	4.678%	$53.3439	$53.34	$53.35	$53.30
Purchase #2	$216.76	12.299%	$243.4193	$243.42	$243.40	$243.40
Purchase #3	$40.76	13.731%	$46.3568	$46.36	$46.35	$46.40
Purchase #4	$80.98	12.550%	$91.143	$91.14	$91.15	$91.10
Purchase #5	$102.91	13.822%	$117.1342	$117.13	$117.15	$117.10
Purchase #6	$187.56	5.839%	$198.5116	$198.51	$198.50	$198.50
Purchase #7	$40.57	12.261%	$45.5443	$45.54	$45.55	$45.50
7 purchase totals =	$720.50		$795.4531	$795.44	$795.45	$795.30