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	$54.62	13.608%	$62.0527	$62.05	$62.05	$62.10
Purchase #2	$64.77	8.225%	$70.0973	$70.10	$70.10	$70.10
Purchase #3	$215.78	6.848%	$230.5566	$230.56	$230.55	$230.60
Purchase #4	$35.63	13.248%	$40.3503	$40.35	$40.35	$40.40
Purchase #5	$218.47	12.276%	$245.2894	$245.29	$245.30	$245.30
Purchase #6	$183.49	7.115%	$196.5453	$196.55	$196.55	$196.50
Purchase #7	$172.71	4.389%	$180.2902	$180.29	$180.30	$180.30
7 purchase totals =	$945.47		$1,025.1818	$1,025.19	$1,025.20	$1,025.30