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	$37.57	9.407%	$41.1042	$41.10	$41.10	$41.10
Purchase #2	$165.88	5.136%	$174.3996	$174.40	$174.40	$174.40
Purchase #3	$129.44	9.781%	$142.1005	$142.10	$142.10	$142.10
Purchase #4	$80.91	8.499%	$87.7865	$87.79	$87.80	$87.80
Purchase #5	$108.64	13.485%	$123.2901	$123.29	$123.30	$123.30
Purchase #6	$95.27	4.783%	$99.8268	$99.83	$99.85	$99.80
Purchase #7	$203.35	12.569%	$228.9091	$228.91	$228.90	$228.90
7 purchase totals =	$821.06		$897.4168	$897.42	$897.45	$897.40