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	$239.69	10.197%	$264.1312	$264.13	$264.15	$264.10
Purchase #2	$42.28	12.322%	$47.4897	$47.49	$47.50	$47.50
Purchase #3	$115.93	12.551%	$130.4804	$130.48	$130.50	$130.50
Purchase #4	$247.66	6.607%	$264.0229	$264.02	$264.00	$264.00
Purchase #5	$166.46	3.281%	$171.9216	$171.92	$171.90	$171.90
Purchase #6	$35.52	5.546%	$37.4899	$37.49	$37.50	$37.50
Purchase #7	$90.89	4.372%	$94.8637	$94.86	$94.85	$94.90
7 purchase totals =	$938.43		$1,010.3994	$1,010.39	$1,010.40	$1,010.40