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	$197.69	4.592%	$206.7679	$206.77	$206.75	$206.80
Purchase #2	$233.70	8.775%	$254.2072	$254.21	$254.20	$254.20
Purchase #3	$134.62	6.801%	$143.7755	$143.78	$143.80	$143.80
Purchase #4	$209.76	5.737%	$221.7939	$221.79	$221.80	$221.80
Purchase #5	$64.52	9.415%	$70.5946	$70.59	$70.60	$70.60
Purchase #6	$143.84	8.547%	$156.134	$156.13	$156.15	$156.10
Purchase #7	$81.83	9.519%	$89.6194	$89.62	$89.60	$89.60
7 purchase totals =	$1,065.96		$1,142.8925	$1,142.89	$1,142.90	$1,142.90