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	$120.48	13.499%	$136.7436	$136.74	$136.75	$136.70
Purchase #2	$38.81	4.460%	$40.5409	$40.54	$40.55	$40.50
Purchase #3	$111.69	5.396%	$117.7168	$117.72	$117.70	$117.70
Purchase #4	$147.30	10.506%	$162.7753	$162.78	$162.80	$162.80
Purchase #5	$201.84	8.443%	$218.8814	$218.88	$218.90	$218.90
Purchase #6	$111.49	4.331%	$116.3186	$116.32	$116.30	$116.30
Purchase #7	$244.90	9.572%	$268.3418	$268.34	$268.35	$268.30
7 purchase totals =	$976.51		$1,061.3184	$1,061.32	$1,061.35	$1,061.20