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	$125.53	8.415%	$136.0933	$136.09	$136.10	$136.10
Purchase #2	$175.88	5.218%	$185.0574	$185.06	$185.05	$185.10
Purchase #3	$20.64	10.186%	$22.7424	$22.74	$22.75	$22.70
Purchase #4	$213.58	4.300%	$222.7639	$222.76	$222.75	$222.80
Purchase #5	$123.74	10.422%	$136.6362	$136.64	$136.65	$136.60
Purchase #6	$156.97	9.230%	$171.4583	$171.46	$171.45	$171.50
Purchase #7	$192.97	8.755%	$209.8645	$209.86	$209.85	$209.90
7 purchase totals =	$1,009.31		$1,084.6160	$1,084.61	$1,084.60	$1,084.70