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	$93.98	12.684%	$105.9004	$105.90	$105.90	$105.90
Purchase #2	$173.46	5.326%	$182.6985	$182.70	$182.70	$182.70
Purchase #3	$37.43	12.867%	$42.2461	$42.25	$42.25	$42.20
Purchase #4	$210.58	6.159%	$223.5496	$223.55	$223.55	$223.50
Purchase #5	$63.52	11.188%	$70.6266	$70.63	$70.65	$70.60
Purchase #6	$203.56	9.201%	$222.2896	$222.29	$222.30	$222.30
Purchase #7	$182.77	13.686%	$207.7839	$207.78	$207.80	$207.80
7 purchase totals =	$965.30		$1,055.0947	$1,055.10	$1,055.15	$1,055.00