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	$168.50	6.223%	$178.9858	$178.99	$179.00	$179.00
Purchase #2	$32.93	12.703%	$37.1131	$37.11	$37.10	$37.10
Purchase #3	$181.44	7.412%	$194.8883	$194.89	$194.90	$194.90
Purchase #4	$12.29	6.399%	$13.0764	$13.08	$13.10	$13.10
Purchase #5	$7.76	8.766%	$8.4402	$8.44	$8.45	$8.40
Purchase #6	$52.50	13.304%	$59.4846	$59.48	$59.50	$59.50
Purchase #7	$211.29	5.130%	$222.1292	$222.13	$222.15	$222.10
7 purchase totals =	$666.71		$714.1176	$714.12	$714.20	$714.10