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	$142.92	11.302%	$159.0728	$159.07	$159.05	$159.10
Purchase #2	$81.50	10.167%	$89.7861	$89.79	$89.80	$89.80
Purchase #3	$148.73	5.392%	$156.7495	$156.75	$156.75	$156.70
Purchase #4	$82.83	6.379%	$88.1137	$88.11	$88.10	$88.10
Purchase #5	$202.69	5.499%	$213.8359	$213.84	$213.85	$213.80
Purchase #6	$211.47	12.503%	$237.9101	$237.91	$237.90	$237.90
Purchase #7	$227.87	10.227%	$251.1743	$251.17	$251.15	$251.20
7 purchase totals =	$1,098.01		$1,196.6424	$1,196.64	$1,196.60	$1,196.60