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	$86.94	3.619%	$90.0864	$90.09	$90.10	$90.10
Purchase #2	$85.92	7.390%	$92.2695	$92.27	$92.25	$92.30
Purchase #3	$136.83	13.554%	$155.3759	$155.38	$155.40	$155.40
Purchase #4	$50.65	13.186%	$57.3287	$57.33	$57.35	$57.30
Purchase #5	$221.30	10.829%	$245.2646	$245.26	$245.25	$245.30
Purchase #6	$187.66	4.665%	$196.4143	$196.41	$196.40	$196.40
Purchase #7	$177.50	13.871%	$202.121	$202.12	$202.10	$202.10
7 purchase totals =	$946.80		$1,038.8604	$1,038.86	$1,038.85	$1,038.90