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	$105.56	8.433%	$114.4619	$114.46	$114.45	$114.50
Purchase #2	$88.51	11.589%	$98.7674	$98.77	$98.75	$98.80
Purchase #3	$246.68	9.813%	$270.8867	$270.89	$270.90	$270.90
Purchase #4	$107.47	4.351%	$112.146	$112.15	$112.15	$112.10
Purchase #5	$42.25	13.421%	$47.9204	$47.92	$47.90	$47.90
Purchase #6	$233.84	4.556%	$244.4938	$244.49	$244.50	$244.50
Purchase #7	$144.93	11.402%	$161.4549	$161.45	$161.45	$161.50
7 purchase totals =	$969.24		$1,050.1311	$1,050.13	$1,050.10	$1,050.20