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	$147.47	4.839%	$154.6061	$154.61	$154.60	$154.60
Purchase #2	$132.38	13.760%	$150.5955	$150.60	$150.60	$150.60
Purchase #3	$58.61	5.381%	$61.7638	$61.76	$61.75	$61.80
Purchase #4	$69.43	4.459%	$72.5259	$72.53	$72.55	$72.50
Purchase #5	$67.94	12.436%	$76.389	$76.39	$76.40	$76.40
Purchase #6	$214.62	6.325%	$228.1947	$228.19	$228.20	$228.20
Purchase #7	$249.81	11.102%	$277.5439	$277.54	$277.55	$277.50
7 purchase totals =	$940.26		$1,021.6189	$1,021.62	$1,021.65	$1,021.60