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	$149.86	8.423%	$162.4827	$162.48	$162.50	$162.50
Purchase #2	$208.51	3.404%	$215.6077	$215.61	$215.60	$215.60
Purchase #3	$166.87	11.112%	$185.4126	$185.41	$185.40	$185.40
Purchase #4	$160.89	4.612%	$168.3102	$168.31	$168.30	$168.30
Purchase #5	$88.79	3.734%	$92.1054	$92.11	$92.10	$92.10
Purchase #6	$7.34	8.421%	$7.9581	$7.96	$7.95	$8.00
Purchase #7	$77.49	5.622%	$81.8465	$81.85	$81.85	$81.80
7 purchase totals =	$859.75		$913.7232	$913.73	$913.70	$913.70