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	$6.91	4.102%	$7.1934	$7.19	$7.20	$7.20
Purchase #2	$25.51	4.156%	$26.5702	$26.57	$26.55	$26.60
Purchase #3	$32.46	4.245%	$33.8379	$33.84	$33.85	$33.80
Purchase #4	$38.33	4.688%	$40.1269	$40.13	$40.15	$40.10
Purchase #5	$165.56	3.784%	$171.8248	$171.82	$171.80	$171.80
Purchase #6	$232.62	4.787%	$243.7555	$243.76	$243.75	$243.80
Purchase #7	$130.68	8.802%	$142.1825	$142.18	$142.20	$142.20
7 purchase totals =	$632.07		$665.4912	$665.49	$665.50	$665.50