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	$164.60	4.506%	$172.0169	$172.02	$172.00	$172.00
Purchase #2	$131.91	11.597%	$147.2076	$147.21	$147.20	$147.20
Purchase #3	$5.58	13.414%	$6.3285	$6.33	$6.35	$6.30
Purchase #4	$29.88	10.588%	$33.0437	$33.04	$33.05	$33.00
Purchase #5	$247.27	3.151%	$255.0615	$255.06	$255.05	$255.10
Purchase #6	$91.39	10.107%	$100.6268	$100.63	$100.65	$100.60
Purchase #7	$180.75	6.806%	$193.0518	$193.05	$193.05	$193.10
7 purchase totals =	$851.38		$907.3368	$907.34	$907.35	$907.30