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	$44.91	7.513%	$48.2841	$48.28	$48.30	$48.30
Purchase #2	$102.90	7.644%	$110.7657	$110.77	$110.75	$110.80
Purchase #3	$103.75	10.629%	$114.7776	$114.78	$114.80	$114.80
Purchase #4	$60.64	6.350%	$64.4906	$64.49	$64.50	$64.50
Purchase #5	$118.39	4.698%	$123.952	$123.95	$123.95	$124.00
Purchase #6	$193.98	13.613%	$220.3865	$220.39	$220.40	$220.40
Purchase #7	$80.56	12.471%	$90.6066	$90.61	$90.60	$90.60
7 purchase totals =	$705.13		$773.2631	$773.27	$773.30	$773.40