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	$135.71	11.183%	$150.8864	$150.89	$150.90	$150.90
Purchase #2	$221.58	5.868%	$234.5823	$234.58	$234.60	$234.60
Purchase #3	$161.53	8.258%	$174.8691	$174.87	$174.85	$174.90
Purchase #4	$166.66	13.121%	$188.5275	$188.53	$188.55	$188.50
Purchase #5	$40.31	5.372%	$42.4755	$42.48	$42.50	$42.50
Purchase #6	$133.33	8.712%	$144.9457	$144.95	$144.95	$144.90
Purchase #7	$173.55	9.330%	$189.7422	$189.74	$189.75	$189.70
7 purchase totals =	$1,032.67		$1,126.0287	$1,126.04	$1,126.10	$1,126.00