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	$190.74	12.762%	$215.0822	$215.08	$215.10	$215.10
Purchase #2	$128.71	11.383%	$143.3611	$143.36	$143.35	$143.40
Purchase #3	$158.56	10.222%	$174.768	$174.77	$174.75	$174.80
Purchase #4	$85.87	5.312%	$90.4314	$90.43	$90.45	$90.40
Purchase #5	$155.64	8.555%	$168.955	$168.96	$168.95	$169.00
Purchase #6	$85.75	3.689%	$88.9133	$88.91	$88.90	$88.90
Purchase #7	$245.79	6.179%	$260.9774	$260.98	$261.00	$261.00
7 purchase totals =	$1,051.06		$1,142.4884	$1,142.49	$1,142.50	$1,142.60