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	$148.63	12.350%	$166.9858	$166.99	$167.00	$167.00
Purchase #2	$136.44	3.394%	$141.0708	$141.07	$141.05	$141.10
Purchase #3	$29.73	9.404%	$32.5258	$32.53	$32.55	$32.50
Purchase #4	$85.34	11.585%	$95.2266	$95.23	$95.25	$95.20
Purchase #5	$141.35	10.399%	$156.049	$156.05	$156.05	$156.00
Purchase #6	$67.53	6.558%	$71.9586	$71.96	$71.95	$72.00
Purchase #7	$19.68	4.789%	$20.6225	$20.62	$20.60	$20.60
7 purchase totals =	$628.70		$684.4391	$684.45	$684.45	$684.40