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	$114.31	11.226%	$127.1424	$127.14	$127.15	$127.10
Purchase #2	$139.26	5.127%	$146.3999	$146.40	$146.40	$146.40
Purchase #3	$82.79	6.634%	$88.2823	$88.28	$88.30	$88.30
Purchase #4	$203.92	6.762%	$217.7091	$217.71	$217.70	$217.70
Purchase #5	$163.37	4.866%	$171.3196	$171.32	$171.30	$171.30
Purchase #6	$180.76	3.841%	$187.703	$187.70	$187.70	$187.70
Purchase #7	$39.74	7.224%	$42.6108	$42.61	$42.60	$42.60
7 purchase totals =	$924.15		$981.1671	$981.16	$981.15	$981.10