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	$138.35	7.402%	$148.5907	$148.59	$148.60	$148.60
Purchase #2	$166.27	13.822%	$189.2518	$189.25	$189.25	$189.30
Purchase #3	$49.89	9.856%	$54.8072	$54.81	$54.80	$54.80
Purchase #4	$30.26	6.578%	$32.2505	$32.25	$32.25	$32.30
Purchase #5	$179.39	11.756%	$200.4791	$200.48	$200.50	$200.50
Purchase #6	$127.68	8.531%	$138.5724	$138.57	$138.55	$138.60
Purchase #7	$231.27	13.732%	$263.028	$263.03	$263.05	$263.00
7 purchase totals =	$923.11		$1,026.9797	$1,026.98	$1,027.00	$1,027.10