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	$96.54	9.130%	$105.3541	$105.35	$105.35	$105.40
Purchase #2	$69.79	12.721%	$78.668	$78.67	$78.65	$78.70
Purchase #3	$89.93	10.651%	$99.5084	$99.51	$99.50	$99.50
Purchase #4	$161.97	6.279%	$172.1401	$172.14	$172.15	$172.10
Purchase #5	$161.76	4.329%	$168.7626	$168.76	$168.75	$168.80
Purchase #6	$41.64	10.539%	$46.0284	$46.03	$46.05	$46.00
Purchase #7	$219.82	8.550%	$238.6146	$238.61	$238.60	$238.60
7 purchase totals =	$841.45		$909.0762	$909.07	$909.05	$909.10