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	$154.46	13.156%	$174.7808	$174.78	$174.80	$174.80
Purchase #2	$33.30	9.297%	$36.3959	$36.40	$36.40	$36.40
Purchase #3	$250.52	10.662%	$277.2304	$277.23	$277.25	$277.20
Purchase #4	$139.29	6.177%	$147.8939	$147.89	$147.90	$147.90
Purchase #5	$238.97	4.857%	$250.5768	$250.58	$250.60	$250.60
Purchase #6	$97.56	4.261%	$101.717	$101.72	$101.70	$101.70
Purchase #7	$82.72	13.456%	$93.8508	$93.85	$93.85	$93.90
7 purchase totals =	$996.82		$1,082.4456	$1,082.45	$1,082.50	$1,082.50