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	$78.96	8.143%	$85.3897	$85.39	$85.40	$85.40
Purchase #2	$70.42	4.266%	$73.4241	$73.42	$73.40	$73.40
Purchase #3	$66.92	7.104%	$71.674	$71.67	$71.65	$71.70
Purchase #4	$153.66	7.444%	$165.0985	$165.10	$165.10	$165.10
Purchase #5	$100.50	6.175%	$106.7059	$106.71	$106.70	$106.70
Purchase #6	$249.43	5.520%	$263.1985	$263.20	$263.20	$263.20
Purchase #7	$25.56	7.229%	$27.4077	$27.41	$27.40	$27.40
7 purchase totals =	$745.45		$792.8984	$792.90	$792.85	$792.90