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	$20.38	11.527%	$22.7292	$22.73	$22.75	$22.70
Purchase #2	$215.32	11.815%	$240.7601	$240.76	$240.75	$240.80
Purchase #3	$227.43	8.578%	$246.9389	$246.94	$246.95	$246.90
Purchase #4	$229.28	12.483%	$257.901	$257.90	$257.90	$257.90
Purchase #5	$30.69	7.693%	$33.051	$33.05	$33.05	$33.10
Purchase #6	$190.27	3.457%	$196.8476	$196.85	$196.85	$196.80
Purchase #7	$107.28	3.818%	$111.376	$111.38	$111.40	$111.40
7 purchase totals =	$1,020.65		$1,109.6038	$1,109.61	$1,109.65	$1,109.60