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	$195.64	13.457%	$221.9673	$221.97	$221.95	$222.00
Purchase #2	$201.86	13.755%	$229.6258	$229.63	$229.65	$229.60
Purchase #3	$36.66	13.590%	$41.6421	$41.64	$41.65	$41.60
Purchase #4	$238.87	11.465%	$266.2564	$266.26	$266.25	$266.30
Purchase #5	$206.54	7.639%	$222.3176	$222.32	$222.30	$222.30
Purchase #6	$68.35	12.265%	$76.7331	$76.73	$76.75	$76.70
Purchase #7	$38.54	9.398%	$42.162	$42.16	$42.15	$42.20
7 purchase totals =	$986.46		$1,100.7043	$1,100.71	$1,100.70	$1,100.70