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	$194.87	13.777%	$221.7172	$221.72	$221.70	$221.70
Purchase #2	$56.34	5.414%	$59.3902	$59.39	$59.40	$59.40
Purchase #3	$175.61	8.520%	$190.572	$190.57	$190.55	$190.60
Purchase #4	$5.32	8.363%	$5.7649	$5.76	$5.75	$5.80
Purchase #5	$133.46	6.801%	$142.5366	$142.54	$142.55	$142.50
Purchase #6	$242.42	9.301%	$264.9675	$264.97	$264.95	$265.00
Purchase #7	$54.55	6.264%	$57.967	$57.97	$57.95	$58.00
7 purchase totals =	$862.57		$942.9154	$942.92	$942.85	$943.00