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	$62.55	5.420%	$65.9402	$65.94	$65.95	$65.90
Purchase #2	$25.91	5.787%	$27.4094	$27.41	$27.40	$27.40
Purchase #3	$209.54	5.518%	$221.1024	$221.10	$221.10	$221.10
Purchase #4	$144.29	9.403%	$157.8576	$157.86	$157.85	$157.90
Purchase #5	$244.37	8.291%	$264.6307	$264.63	$264.65	$264.60
Purchase #6	$98.72	6.839%	$105.4715	$105.47	$105.45	$105.50
Purchase #7	$68.72	7.320%	$73.7503	$73.75	$73.75	$73.80
7 purchase totals =	$854.10		$916.1621	$916.16	$916.15	$916.20