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	$150.47	9.735%	$165.1183	$165.12	$165.10	$165.10
Purchase #2	$94.73	4.694%	$99.1766	$99.18	$99.20	$99.20
Purchase #3	$233.66	11.400%	$260.2972	$260.30	$260.30	$260.30
Purchase #4	$213.30	4.708%	$223.3422	$223.34	$223.35	$223.30
Purchase #5	$32.88	10.212%	$36.2377	$36.24	$36.25	$36.20
Purchase #6	$91.54	13.451%	$103.853	$103.85	$103.85	$103.90
Purchase #7	$242.25	5.851%	$256.424	$256.42	$256.40	$256.40
7 purchase totals =	$1,058.83		$1,144.4490	$1,144.45	$1,144.45	$1,144.40