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	$40.28	12.540%	$45.3311	$45.33	$45.35	$45.30
Purchase #2	$90.82	10.451%	$100.3116	$100.31	$100.30	$100.30
Purchase #3	$145.77	10.329%	$160.8266	$160.83	$160.85	$160.80
Purchase #4	$55.61	3.838%	$57.7443	$57.74	$57.75	$57.70
Purchase #5	$217.64	12.476%	$244.7928	$244.79	$244.80	$244.80
Purchase #6	$81.26	4.802%	$85.1621	$85.16	$85.15	$85.20
Purchase #7	$60.68	12.360%	$68.18	$68.18	$68.20	$68.20
7 purchase totals =	$692.06		$762.3485	$762.34	$762.40	$762.30