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	$126.73	13.734%	$144.1351	$144.14	$144.15	$144.10
Purchase #2	$78.94	11.593%	$88.0915	$88.09	$88.10	$88.10
Purchase #3	$172.37	7.513%	$185.3202	$185.32	$185.30	$185.30
Purchase #4	$138.71	4.425%	$144.8479	$144.85	$144.85	$144.80
Purchase #5	$197.95	6.695%	$211.2028	$211.20	$211.20	$211.20
Purchase #6	$176.32	3.850%	$183.1083	$183.11	$183.10	$183.10
Purchase #7	$161.87	3.673%	$167.8155	$167.82	$167.80	$167.80
7 purchase totals =	$1,052.89		$1,124.5213	$1,124.53	$1,124.50	$1,124.40