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	$146.63	7.426%	$157.5187	$157.52	$157.50	$157.50
Purchase #2	$156.63	8.200%	$169.4737	$169.47	$169.45	$169.50
Purchase #3	$51.72	13.335%	$58.6169	$58.62	$58.60	$58.60
Purchase #4	$79.85	13.470%	$90.6058	$90.61	$90.60	$90.60
Purchase #5	$18.35	9.234%	$20.0444	$20.04	$20.05	$20.00
Purchase #6	$147.44	13.521%	$167.3754	$167.38	$167.40	$167.40
Purchase #7	$98.68	6.446%	$105.0409	$105.04	$105.05	$105.00
7 purchase totals =	$699.30		$768.6758	$768.68	$768.65	$768.60