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	$17.59	8.309%	$19.0516	$19.05	$19.05	$19.10
Purchase #2	$98.77	10.858%	$109.4944	$109.49	$109.50	$109.50
Purchase #3	$85.68	11.629%	$95.6437	$95.64	$95.65	$95.60
Purchase #4	$246.93	10.776%	$273.5392	$273.54	$273.55	$273.50
Purchase #5	$129.33	13.569%	$146.8788	$146.88	$146.90	$146.90
Purchase #6	$244.73	6.758%	$261.2689	$261.27	$261.25	$261.30
Purchase #7	$180.26	11.170%	$200.395	$200.40	$200.40	$200.40
7 purchase totals =	$1,003.29		$1,106.2716	$1,106.27	$1,106.30	$1,106.30