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	$124.97	7.540%	$134.3927	$134.39	$134.40	$134.40
Purchase #2	$99.85	10.506%	$110.3402	$110.34	$110.35	$110.30
Purchase #3	$242.92	4.356%	$253.5016	$253.50	$253.50	$253.50
Purchase #4	$117.58	13.844%	$133.8578	$133.86	$133.85	$133.90
Purchase #5	$54.83	12.860%	$61.8811	$61.88	$61.90	$61.90
Purchase #6	$127.92	10.545%	$141.4092	$141.41	$141.40	$141.40
Purchase #7	$84.57	7.305%	$90.7478	$90.75	$90.75	$90.70
7 purchase totals =	$852.64		$926.1304	$926.13	$926.15	$926.10