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	$49.57	13.653%	$56.3378	$56.34	$56.35	$56.30
Purchase #2	$153.49	11.557%	$171.2288	$171.23	$171.25	$171.20
Purchase #3	$31.29	7.808%	$33.7331	$33.73	$33.75	$33.70
Purchase #4	$241.35	8.278%	$261.329	$261.33	$261.35	$261.30
Purchase #5	$216.48	3.690%	$224.4681	$224.47	$224.45	$224.50
Purchase #6	$156.38	6.786%	$166.9919	$166.99	$167.00	$167.00
Purchase #7	$83.30	6.408%	$88.6379	$88.64	$88.65	$88.60
7 purchase totals =	$931.86		$1,002.7266	$1,002.73	$1,002.80	$1,002.60