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	$207.37	4.112%	$215.8971	$215.90	$215.90	$215.90
Purchase #2	$18.78	9.277%	$20.5222	$20.52	$20.50	$20.50
Purchase #3	$211.76	13.488%	$240.3222	$240.32	$240.30	$240.30
Purchase #4	$55.62	12.862%	$62.7738	$62.77	$62.75	$62.80
Purchase #5	$168.59	4.136%	$175.5629	$175.56	$175.55	$175.60
Purchase #6	$126.56	8.477%	$137.2885	$137.29	$137.30	$137.30
Purchase #7	$195.60	4.676%	$204.7463	$204.75	$204.75	$204.70
7 purchase totals =	$984.28		$1,057.1130	$1,057.11	$1,057.05	$1,057.10