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	$78.98	6.289%	$83.9471	$83.95	$83.95	$83.90
Purchase #2	$75.73	12.758%	$85.3916	$85.39	$85.40	$85.40
Purchase #3	$199.76	10.558%	$220.8507	$220.85	$220.85	$220.90
Purchase #4	$226.57	5.862%	$239.8515	$239.85	$239.85	$239.90
Purchase #5	$103.91	7.279%	$111.4736	$111.47	$111.45	$111.50
Purchase #6	$47.34	13.553%	$53.756	$53.76	$53.75	$53.80
Purchase #7	$153.89	3.364%	$159.0669	$159.07	$159.05	$159.10
7 purchase totals =	$886.18		$954.3374	$954.34	$954.30	$954.50