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	$149.65	4.661%	$156.6252	$156.63	$156.65	$156.60
Purchase #2	$33.78	12.192%	$37.8985	$37.90	$37.90	$37.90
Purchase #3	$60.76	9.812%	$66.7218	$66.72	$66.70	$66.70
Purchase #4	$233.59	6.804%	$249.4835	$249.48	$249.50	$249.50
Purchase #5	$184.93	4.148%	$192.6009	$192.60	$192.60	$192.60
Purchase #6	$138.78	13.563%	$157.6027	$157.60	$157.60	$157.60
Purchase #7	$54.73	12.424%	$61.5297	$61.53	$61.55	$61.50
7 purchase totals =	$856.22		$922.4623	$922.46	$922.50	$922.40