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	$13.43	10.560%	$14.8482	$14.85	$14.85	$14.80
Purchase #2	$75.91	3.554%	$78.6078	$78.61	$78.60	$78.60
Purchase #3	$75.56	13.407%	$85.6903	$85.69	$85.70	$85.70
Purchase #4	$232.88	8.804%	$253.3828	$253.38	$253.40	$253.40
Purchase #5	$201.71	9.495%	$220.8624	$220.86	$220.85	$220.90
Purchase #6	$131.44	10.156%	$144.789	$144.79	$144.80	$144.80
Purchase #7	$79.52	12.121%	$89.1586	$89.16	$89.15	$89.20
7 purchase totals =	$810.45		$887.3391	$887.34	$887.35	$887.40