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	$215.38	8.344%	$233.3513	$233.35	$233.35	$233.40
Purchase #2	$243.65	4.447%	$254.4851	$254.49	$254.50	$254.50
Purchase #3	$78.93	4.616%	$82.5734	$82.57	$82.55	$82.60
Purchase #4	$85.41	8.784%	$92.9124	$92.91	$92.90	$92.90
Purchase #5	$13.30	13.569%	$15.1047	$15.10	$15.10	$15.10
Purchase #6	$109.68	12.407%	$123.288	$123.29	$123.30	$123.30
Purchase #7	$151.27	11.559%	$168.7553	$168.76	$168.75	$168.80
7 purchase totals =	$897.62		$970.4702	$970.47	$970.45	$970.60