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	$182.38	6.536%	$194.3004	$194.30	$194.30	$194.30
Purchase #2	$52.34	13.784%	$59.5545	$59.55	$59.55	$59.60
Purchase #3	$88.59	4.483%	$92.5615	$92.56	$92.55	$92.60
Purchase #4	$208.25	7.426%	$223.7146	$223.71	$223.70	$223.70
Purchase #5	$87.25	12.852%	$98.4634	$98.46	$98.45	$98.50
Purchase #6	$95.82	10.243%	$105.6348	$105.63	$105.65	$105.60
Purchase #7	$185.76	6.158%	$197.1991	$197.20	$197.20	$197.20
7 purchase totals =	$900.39		$971.4283	$971.41	$971.40	$971.50