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	$64.35	8.633%	$69.9053	$69.91	$69.90	$69.90
Purchase #2	$204.28	8.842%	$222.3424	$222.34	$222.35	$222.30
Purchase #3	$196.78	13.666%	$223.672	$223.67	$223.65	$223.70
Purchase #4	$75.80	3.410%	$78.3848	$78.38	$78.40	$78.40
Purchase #5	$31.73	5.758%	$33.557	$33.56	$33.55	$33.60
Purchase #6	$88.64	12.126%	$99.3885	$99.39	$99.40	$99.40
Purchase #7	$250.68	7.827%	$270.3007	$270.30	$270.30	$270.30
7 purchase totals =	$912.26		$997.5507	$997.55	$997.55	$997.60