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	$108.40	4.502%	$113.2802	$113.28	$113.30	$113.30
Purchase #2	$51.34	8.288%	$55.5951	$55.60	$55.60	$55.60
Purchase #3	$139.28	4.783%	$145.9418	$145.94	$145.95	$145.90
Purchase #4	$72.52	8.496%	$78.6813	$78.68	$78.70	$78.70
Purchase #5	$172.33	11.653%	$192.4116	$192.41	$192.40	$192.40
Purchase #6	$66.88	7.272%	$71.7435	$71.74	$71.75	$71.70
Purchase #7	$79.25	9.244%	$86.5759	$86.58	$86.60	$86.60
7 purchase totals =	$690.00		$744.2294	$744.23	$744.30	$744.20