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	$147.44	4.753%	$154.4478	$154.45	$154.45	$154.40
Purchase #2	$18.88	4.590%	$19.7466	$19.75	$19.75	$19.70
Purchase #3	$94.33	8.865%	$102.6924	$102.69	$102.70	$102.70
Purchase #4	$75.60	9.668%	$82.909	$82.91	$82.90	$82.90
Purchase #5	$80.53	4.222%	$83.93	$83.93	$83.95	$83.90
Purchase #6	$86.39	3.229%	$89.1795	$89.18	$89.20	$89.20
Purchase #7	$116.49	3.420%	$120.474	$120.47	$120.45	$120.50
7 purchase totals =	$619.66		$653.3793	$653.38	$653.40	$653.30