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	$152.86	12.165%	$171.4554	$171.46	$171.45	$171.50
Purchase #2	$106.73	5.856%	$112.9801	$112.98	$113.00	$113.00
Purchase #3	$27.42	13.208%	$31.0416	$31.04	$31.05	$31.00
Purchase #4	$35.89	6.859%	$38.3517	$38.35	$38.35	$38.40
Purchase #5	$239.55	13.739%	$272.4618	$272.46	$272.45	$272.50
Purchase #6	$157.87	4.537%	$165.0326	$165.03	$165.05	$165.00
Purchase #7	$52.54	6.422%	$55.9141	$55.91	$55.90	$55.90
7 purchase totals =	$772.86		$847.2373	$847.23	$847.25	$847.30