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	$233.79	7.721%	$251.8409	$251.84	$251.85	$251.80
Purchase #2	$115.47	8.793%	$125.6233	$125.62	$125.60	$125.60
Purchase #3	$150.94	10.235%	$166.3887	$166.39	$166.40	$166.40
Purchase #4	$76.46	8.416%	$82.8949	$82.89	$82.90	$82.90
Purchase #5	$33.62	5.308%	$35.4045	$35.40	$35.40	$35.40
Purchase #6	$55.33	7.639%	$59.5567	$59.56	$59.55	$59.60
Purchase #7	$58.56	10.573%	$64.7515	$64.75	$64.75	$64.80
7 purchase totals =	$724.17		$786.4605	$786.45	$786.45	$786.50