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	$109.38	3.170%	$112.8473	$112.85	$112.85	$112.80
Purchase #2	$216.98	13.199%	$245.6192	$245.62	$245.60	$245.60
Purchase #3	$234.48	8.549%	$254.5257	$254.53	$254.55	$254.50
Purchase #4	$42.72	3.279%	$44.1208	$44.12	$44.10	$44.10
Purchase #5	$122.82	13.526%	$139.4326	$139.43	$139.45	$139.40
Purchase #6	$149.49	4.505%	$156.2245	$156.22	$156.20	$156.20
Purchase #7	$145.42	10.611%	$160.8505	$160.85	$160.85	$160.90
7 purchase totals =	$1,021.29		$1,113.6206	$1,113.62	$1,113.60	$1,113.50