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	$192.28	8.838%	$209.2737	$209.27	$209.25	$209.30
Purchase #2	$49.76	6.741%	$53.1143	$53.11	$53.10	$53.10
Purchase #3	$82.57	10.788%	$91.4777	$91.48	$91.50	$91.50
Purchase #4	$5.38	6.190%	$5.713	$5.71	$5.70	$5.70
Purchase #5	$133.56	11.264%	$148.6042	$148.60	$148.60	$148.60
Purchase #6	$204.57	6.758%	$218.3948	$218.39	$218.40	$218.40
Purchase #7	$38.31	6.860%	$40.9381	$40.94	$40.95	$40.90
7 purchase totals =	$706.43		$767.5158	$767.50	$767.50	$767.50