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	$168.30	3.565%	$174.2999	$174.30	$174.30	$174.30
Purchase #2	$125.65	10.468%	$138.803	$138.80	$138.80	$138.80
Purchase #3	$130.44	10.529%	$144.174	$144.17	$144.15	$144.20
Purchase #4	$166.65	4.800%	$174.6492	$174.65	$174.65	$174.60
Purchase #5	$170.31	5.632%	$179.9019	$179.90	$179.90	$179.90
Purchase #6	$56.71	5.177%	$59.6459	$59.65	$59.65	$59.60
Purchase #7	$127.34	9.864%	$139.9008	$139.90	$139.90	$139.90
7 purchase totals =	$945.40		$1,011.3747	$1,011.37	$1,011.35	$1,011.30