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	$198.77	11.342%	$221.3145	$221.31	$221.30	$221.30
Purchase #2	$53.61	3.706%	$55.5968	$55.60	$55.60	$55.60
Purchase #3	$82.50	9.760%	$90.552	$90.55	$90.55	$90.60
Purchase #4	$137.39	5.407%	$144.8187	$144.82	$144.80	$144.80
Purchase #5	$191.63	9.317%	$209.4842	$209.48	$209.50	$209.50
Purchase #6	$144.71	4.571%	$151.3247	$151.32	$151.30	$151.30
Purchase #7	$228.55	5.398%	$240.8871	$240.89	$240.90	$240.90
7 purchase totals =	$1,037.16		$1,113.9780	$1,113.97	$1,113.95	$1,114.00