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	$228.47	4.116%	$237.8738	$237.87	$237.85	$237.90
Purchase #2	$80.91	11.345%	$90.0892	$90.09	$90.10	$90.10
Purchase #3	$85.69	9.539%	$93.864	$93.86	$93.85	$93.90
Purchase #4	$165.61	12.310%	$185.9966	$186.00	$186.00	$186.00
Purchase #5	$190.71	7.183%	$204.4087	$204.41	$204.40	$204.40
Purchase #6	$187.86	4.456%	$196.231	$196.23	$196.25	$196.20
Purchase #7	$70.99	9.167%	$77.4977	$77.50	$77.50	$77.50
7 purchase totals =	$1,010.24		$1,085.9610	$1,085.96	$1,085.95	$1,086.00