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	$238.53	11.635%	$266.283	$266.28	$266.30	$266.30
Purchase #2	$11.72	10.736%	$12.9783	$12.98	$13.00	$13.00
Purchase #3	$169.45	6.797%	$180.9675	$180.97	$180.95	$181.00
Purchase #4	$249.56	13.851%	$284.1266	$284.13	$284.15	$284.10
Purchase #5	$84.25	7.297%	$90.3977	$90.40	$90.40	$90.40
Purchase #6	$113.35	3.600%	$117.4306	$117.43	$117.45	$117.40
Purchase #7	$93.92	5.861%	$99.4247	$99.42	$99.40	$99.40
7 purchase totals =	$960.78		$1,051.6084	$1,051.61	$1,051.65	$1,051.60