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	$143.43	7.308%	$153.9119	$153.91	$153.90	$153.90
Purchase #2	$234.92	8.764%	$255.5084	$255.51	$255.50	$255.50
Purchase #3	$216.85	13.384%	$245.8732	$245.87	$245.85	$245.90
Purchase #4	$77.84	9.402%	$85.1585	$85.16	$85.15	$85.20
Purchase #5	$198.79	6.598%	$211.9062	$211.91	$211.90	$211.90
Purchase #6	$239.56	10.682%	$265.1498	$265.15	$265.15	$265.10
Purchase #7	$79.37	6.407%	$84.4552	$84.46	$84.45	$84.50
7 purchase totals =	$1,190.76		$1,301.9632	$1,301.97	$1,301.90	$1,302.00