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	$35.75	6.705%	$38.147	$38.15	$38.15	$38.10
Purchase #2	$31.46	5.830%	$33.2941	$33.29	$33.30	$33.30
Purchase #3	$204.64	12.418%	$230.0522	$230.05	$230.05	$230.10
Purchase #4	$71.63	9.380%	$78.3489	$78.35	$78.35	$78.30
Purchase #5	$36.35	3.518%	$37.6288	$37.63	$37.65	$37.60
Purchase #6	$11.40	5.384%	$12.0138	$12.01	$12.00	$12.00
Purchase #7	$94.51	5.347%	$99.5634	$99.56	$99.55	$99.60
7 purchase totals =	$485.74		$529.0482	$529.04	$529.05	$529.00