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	$186.37	5.621%	$196.8459	$196.85	$196.85	$196.80
Purchase #2	$221.65	3.610%	$229.6516	$229.65	$229.65	$229.70
Purchase #3	$29.96	9.292%	$32.7439	$32.74	$32.75	$32.70
Purchase #4	$117.89	11.316%	$131.2304	$131.23	$131.25	$131.20
Purchase #5	$53.48	5.140%	$56.2289	$56.23	$56.25	$56.20
Purchase #6	$140.70	7.804%	$151.6802	$151.68	$151.70	$151.70
Purchase #7	$233.43	12.400%	$262.3753	$262.38	$262.40	$262.40
7 purchase totals =	$983.48		$1,060.7562	$1,060.76	$1,060.85	$1,060.70