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	$189.56	5.593%	$200.1621	$200.16	$200.15	$200.20
Purchase #2	$234.71	12.199%	$263.3423	$263.34	$263.35	$263.30
Purchase #3	$56.98	3.748%	$59.1156	$59.12	$59.10	$59.10
Purchase #4	$102.70	11.332%	$114.338	$114.34	$114.35	$114.30
Purchase #5	$114.69	7.766%	$123.5968	$123.60	$123.60	$123.60
Purchase #6	$50.70	11.539%	$56.5503	$56.55	$56.55	$56.60
Purchase #7	$172.80	7.678%	$186.0676	$186.07	$186.05	$186.10
7 purchase totals =	$922.14		$1,003.1727	$1,003.18	$1,003.15	$1,003.20