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	$135.66	4.240%	$141.412	$141.41	$141.40	$141.40
Purchase #2	$247.97	4.267%	$258.5509	$258.55	$258.55	$258.60
Purchase #3	$75.90	9.202%	$82.8843	$82.88	$82.90	$82.90
Purchase #4	$97.27	11.278%	$108.2401	$108.24	$108.25	$108.20
Purchase #5	$208.42	3.385%	$215.475	$215.48	$215.50	$215.50
Purchase #6	$120.92	13.815%	$137.6251	$137.63	$137.65	$137.60
Purchase #7	$116.77	11.564%	$130.2733	$130.27	$130.25	$130.30
7 purchase totals =	$1,002.91		$1,074.4607	$1,074.46	$1,074.50	$1,074.50