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	$112.37	13.479%	$127.5164	$127.52	$127.50	$127.50
Purchase #2	$209.88	8.751%	$228.2466	$228.25	$228.25	$228.20
Purchase #3	$149.38	13.756%	$169.9287	$169.93	$169.95	$169.90
Purchase #4	$125.51	12.568%	$141.2841	$141.28	$141.30	$141.30
Purchase #5	$190.29	3.780%	$197.483	$197.48	$197.50	$197.50
Purchase #6	$69.90	12.530%	$78.6585	$78.66	$78.65	$78.70
Purchase #7	$218.81	4.767%	$229.2407	$229.24	$229.25	$229.20
7 purchase totals =	$1,076.14		$1,172.3580	$1,172.36	$1,172.40	$1,172.30