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	$228.28	5.457%	$240.7372	$240.74	$240.75	$240.70
Purchase #2	$235.72	11.555%	$262.9574	$262.96	$262.95	$263.00
Purchase #3	$201.56	13.766%	$229.3067	$229.31	$229.30	$229.30
Purchase #4	$54.48	6.124%	$57.8164	$57.82	$57.80	$57.80
Purchase #5	$80.33	13.745%	$91.3714	$91.37	$91.35	$91.40
Purchase #6	$150.28	13.464%	$170.5137	$170.51	$170.50	$170.50
Purchase #7	$18.83	8.744%	$20.4765	$20.48	$20.50	$20.50
7 purchase totals =	$969.48		$1,073.1793	$1,073.19	$1,073.15	$1,073.20