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	$145.55	3.348%	$150.423	$150.42	$150.40	$150.40
Purchase #2	$111.28	4.445%	$116.2264	$116.23	$116.25	$116.20
Purchase #3	$16.29	11.248%	$18.1223	$18.12	$18.10	$18.10
Purchase #4	$218.88	3.478%	$226.4926	$226.49	$226.50	$226.50
Purchase #5	$80.45	11.734%	$89.89	$89.89	$89.90	$89.90
Purchase #6	$143.46	3.644%	$148.6877	$148.69	$148.70	$148.70
Purchase #7	$47.58	3.575%	$49.281	$49.28	$49.30	$49.30
7 purchase totals =	$763.49		$799.1230	$799.12	$799.15	$799.10