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	$43.86	7.110%	$46.9784	$46.98	$47.00	$47.00
Purchase #2	$93.44	6.568%	$99.5771	$99.58	$99.60	$99.60
Purchase #3	$240.36	9.788%	$263.8864	$263.89	$263.90	$263.90
Purchase #4	$185.98	3.149%	$191.8365	$191.84	$191.85	$191.80
Purchase #5	$168.63	12.409%	$189.5553	$189.56	$189.55	$189.60
Purchase #6	$74.57	5.313%	$78.5319	$78.53	$78.55	$78.50
Purchase #7	$98.53	5.156%	$103.6102	$103.61	$103.60	$103.60
7 purchase totals =	$905.37		$973.9758	$973.99	$974.05	$974.00