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	$40.61	13.487%	$46.0871	$46.09	$46.10	$46.10
Purchase #2	$184.34	3.102%	$190.0582	$190.06	$190.05	$190.10
Purchase #3	$229.37	8.166%	$248.1004	$248.10	$248.10	$248.10
Purchase #4	$80.88	10.167%	$89.1031	$89.10	$89.10	$89.10
Purchase #5	$98.52	4.314%	$102.7702	$102.77	$102.75	$102.80
Purchase #6	$104.56	12.559%	$117.6917	$117.69	$117.70	$117.70
Purchase #7	$148.33	13.730%	$168.6957	$168.70	$168.70	$168.70
7 purchase totals =	$886.61		$962.5064	$962.51	$962.50	$962.60