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	$175.46	12.194%	$196.8556	$196.86	$196.85	$196.90
Purchase #2	$214.90	3.406%	$222.2195	$222.22	$222.20	$222.20
Purchase #3	$30.25	6.626%	$32.2544	$32.25	$32.25	$32.30
Purchase #4	$40.27	9.168%	$43.962	$43.96	$43.95	$44.00
Purchase #5	$239.28	8.517%	$259.6595	$259.66	$259.65	$259.70
Purchase #6	$104.60	4.427%	$109.2306	$109.23	$109.25	$109.20
Purchase #7	$32.57	3.586%	$33.738	$33.74	$33.75	$33.70
7 purchase totals =	$837.33		$897.9196	$897.92	$897.90	$898.00