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	$107.66	11.743%	$120.3025	$120.30	$120.30	$120.30
Purchase #2	$197.27	12.291%	$221.5165	$221.52	$221.50	$221.50
Purchase #3	$67.61	8.861%	$73.6009	$73.60	$73.60	$73.60
Purchase #4	$190.63	9.432%	$208.6102	$208.61	$208.60	$208.60
Purchase #5	$97.67	3.146%	$100.7427	$100.74	$100.75	$100.70
Purchase #6	$82.75	4.844%	$86.7584	$86.76	$86.75	$86.80
Purchase #7	$144.74	4.225%	$150.8553	$150.86	$150.85	$150.90
7 purchase totals =	$888.33		$962.3865	$962.39	$962.35	$962.40