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	$52.53	12.463%	$59.0768	$59.08	$59.10	$59.10
Purchase #2	$22.31	13.220%	$25.2594	$25.26	$25.25	$25.30
Purchase #3	$41.71	9.623%	$45.7238	$45.72	$45.70	$45.70
Purchase #4	$110.42	8.385%	$119.6787	$119.68	$119.70	$119.70
Purchase #5	$119.80	6.183%	$127.2072	$127.21	$127.20	$127.20
Purchase #6	$162.32	3.706%	$168.3356	$168.34	$168.35	$168.30
Purchase #7	$35.82	3.636%	$37.1224	$37.12	$37.10	$37.10
7 purchase totals =	$544.91		$582.4039	$582.41	$582.40	$582.40