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	$247.88	10.454%	$273.7934	$273.79	$273.80	$273.80
Purchase #2	$91.50	7.187%	$98.0761	$98.08	$98.10	$98.10
Purchase #3	$204.69	8.341%	$221.7632	$221.76	$221.75	$221.80
Purchase #4	$85.93	5.781%	$90.8976	$90.90	$90.90	$90.90
Purchase #5	$43.37	11.677%	$48.4343	$48.43	$48.45	$48.40
Purchase #6	$86.75	10.310%	$95.6939	$95.69	$95.70	$95.70
Purchase #7	$175.32	3.671%	$181.756	$181.76	$181.75	$181.80
7 purchase totals =	$935.44		$1,010.4145	$1,010.41	$1,010.45	$1,010.50