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	$109.87	6.424%	$116.928	$116.93	$116.95	$116.90
Purchase #2	$124.56	5.431%	$131.3249	$131.32	$131.30	$131.30
Purchase #3	$97.41	5.622%	$102.8864	$102.89	$102.90	$102.90
Purchase #4	$174.50	11.486%	$194.5431	$194.54	$194.55	$194.50
Purchase #5	$197.47	12.103%	$221.3698	$221.37	$221.35	$221.40
Purchase #6	$142.76	13.125%	$161.4973	$161.50	$161.50	$161.50
Purchase #7	$147.29	4.108%	$153.3407	$153.34	$153.35	$153.30
7 purchase totals =	$993.86		$1,081.8902	$1,081.89	$1,081.90	$1,081.80