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	$50.37	7.329%	$54.0616	$54.06	$54.05	$54.10
Purchase #2	$50.59	3.742%	$52.4831	$52.48	$52.50	$52.50
Purchase #3	$249.60	5.703%	$263.8347	$263.83	$263.85	$263.80
Purchase #4	$211.82	5.328%	$223.1058	$223.11	$223.10	$223.10
Purchase #5	$150.78	11.727%	$168.462	$168.46	$168.45	$168.50
Purchase #6	$160.72	5.616%	$169.746	$169.75	$169.75	$169.70
Purchase #7	$223.29	4.862%	$234.1464	$234.15	$234.15	$234.10
7 purchase totals =	$1,097.17		$1,165.8396	$1,165.84	$1,165.85	$1,165.80