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	$167.75	3.260%	$173.2187	$173.22	$173.20	$173.20
Purchase #2	$214.40	7.867%	$231.2668	$231.27	$231.25	$231.30
Purchase #3	$43.42	4.728%	$45.4729	$45.47	$45.45	$45.50
Purchase #4	$71.59	3.418%	$74.0369	$74.04	$74.05	$74.00
Purchase #5	$147.46	12.412%	$165.7627	$165.76	$165.75	$165.80
Purchase #6	$38.53	10.294%	$42.4963	$42.50	$42.50	$42.50
Purchase #7	$234.36	6.742%	$250.1606	$250.16	$250.15	$250.20
7 purchase totals =	$917.51		$982.4149	$982.42	$982.35	$982.50