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	$29.55	9.465%	$32.3469	$32.35	$32.35	$32.30
Purchase #2	$114.44	5.277%	$120.479	$120.48	$120.50	$120.50
Purchase #3	$128.32	11.355%	$142.8907	$142.89	$142.90	$142.90
Purchase #4	$158.40	12.675%	$178.4772	$178.48	$178.50	$178.50
Purchase #5	$91.92	11.131%	$102.1516	$102.15	$102.15	$102.20
Purchase #6	$116.54	9.146%	$127.1987	$127.20	$127.20	$127.20
Purchase #7	$153.64	12.551%	$172.9234	$172.92	$172.90	$172.90
7 purchase totals =	$792.81		$876.4675	$876.47	$876.50	$876.50