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	$95.48	8.623%	$103.7132	$103.71	$103.70	$103.70
Purchase #2	$171.32	11.867%	$191.6505	$191.65	$191.65	$191.70
Purchase #3	$98.42	6.613%	$104.9285	$104.93	$104.95	$104.90
Purchase #4	$156.69	3.205%	$161.7119	$161.71	$161.70	$161.70
Purchase #5	$103.83	7.781%	$111.909	$111.91	$111.90	$111.90
Purchase #6	$104.62	9.525%	$114.5851	$114.59	$114.60	$114.60
Purchase #7	$128.65	10.173%	$141.7376	$141.74	$141.75	$141.70
7 purchase totals =	$859.01		$930.2358	$930.24	$930.25	$930.20