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	$41.41	13.442%	$46.9763	$46.98	$47.00	$47.00
Purchase #2	$149.65	10.837%	$165.8676	$165.87	$165.85	$165.90
Purchase #3	$93.53	12.869%	$105.5664	$105.57	$105.55	$105.60
Purchase #4	$230.43	3.566%	$238.6471	$238.65	$238.65	$238.60
Purchase #5	$80.74	11.723%	$90.2052	$90.21	$90.20	$90.20
Purchase #6	$61.53	5.407%	$64.8569	$64.86	$64.85	$64.90
Purchase #7	$242.33	12.197%	$271.887	$271.89	$271.90	$271.90
7 purchase totals =	$899.62		$984.0065	$984.03	$984.00	$984.10