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	$85.25	4.114%	$88.7572	$88.76	$88.75	$88.80
Purchase #2	$29.39	10.372%	$32.4383	$32.44	$32.45	$32.40
Purchase #3	$150.96	11.194%	$167.8585	$167.86	$167.85	$167.90
Purchase #4	$232.72	13.776%	$264.7795	$264.78	$264.80	$264.80
Purchase #5	$36.73	6.460%	$39.1028	$39.10	$39.10	$39.10
Purchase #6	$213.70	6.338%	$227.2443	$227.24	$227.25	$227.20
Purchase #7	$184.74	6.447%	$196.6502	$196.65	$196.65	$196.70
7 purchase totals =	$933.49		$1,016.8308	$1,016.83	$1,016.85	$1,016.90