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	$181.25	9.508%	$198.4833	$198.48	$198.50	$198.50
Purchase #2	$39.40	12.374%	$44.2754	$44.28	$44.30	$44.30
Purchase #3	$51.27	11.847%	$57.344	$57.34	$57.35	$57.30
Purchase #4	$200.64	6.320%	$213.3204	$213.32	$213.30	$213.30
Purchase #5	$192.41	13.622%	$218.6201	$218.62	$218.60	$218.60
Purchase #6	$82.31	8.472%	$89.2833	$89.28	$89.30	$89.30
Purchase #7	$173.69	12.819%	$195.9553	$195.96	$195.95	$196.00
7 purchase totals =	$920.97		$1,017.2818	$1,017.28	$1,017.30	$1,017.30