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	$234.94	3.535%	$243.2451	$243.25	$243.25	$243.20
Purchase #2	$41.45	9.416%	$45.3529	$45.35	$45.35	$45.40
Purchase #3	$111.33	4.449%	$116.2831	$116.28	$116.30	$116.30
Purchase #4	$181.90	9.415%	$199.0259	$199.03	$199.05	$199.00
Purchase #5	$55.71	7.684%	$59.9908	$59.99	$60.00	$60.00
Purchase #6	$146.43	13.311%	$165.9213	$165.92	$165.90	$165.90
Purchase #7	$165.49	10.526%	$182.9095	$182.91	$182.90	$182.90
7 purchase totals =	$937.25		$1,012.7286	$1,012.73	$1,012.75	$1,012.70