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	$249.40	9.619%	$273.3898	$273.39	$273.40	$273.40
Purchase #2	$68.56	7.165%	$73.4723	$73.47	$73.45	$73.50
Purchase #3	$114.82	5.219%	$120.8125	$120.81	$120.80	$120.80
Purchase #4	$179.27	12.625%	$201.9028	$201.90	$201.90	$201.90
Purchase #5	$186.37	5.644%	$196.8887	$196.89	$196.90	$196.90
Purchase #6	$77.81	11.592%	$86.8297	$86.83	$86.85	$86.80
Purchase #7	$95.41	4.345%	$99.5556	$99.56	$99.55	$99.60
7 purchase totals =	$971.64		$1,052.8514	$1,052.85	$1,052.85	$1,052.90