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	$56.31	3.464%	$58.2606	$58.26	$58.25	$58.30
Purchase #2	$216.71	8.395%	$234.9028	$234.90	$234.90	$234.90
Purchase #3	$27.43	5.129%	$28.8369	$28.84	$28.85	$28.80
Purchase #4	$148.61	11.535%	$165.7522	$165.75	$165.75	$165.80
Purchase #5	$95.75	11.670%	$106.924	$106.92	$106.90	$106.90
Purchase #6	$124.42	10.806%	$137.8648	$137.86	$137.85	$137.90
Purchase #7	$81.98	9.671%	$89.9083	$89.91	$89.90	$89.90
7 purchase totals =	$751.21		$822.4496	$822.44	$822.40	$822.50