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	$59.58	9.405%	$65.1835	$65.18	$65.20	$65.20
Purchase #2	$33.92	11.578%	$37.8473	$37.85	$37.85	$37.80
Purchase #3	$56.33	7.498%	$60.5536	$60.55	$60.55	$60.60
Purchase #4	$16.59	12.159%	$18.6072	$18.61	$18.60	$18.60
Purchase #5	$67.60	6.277%	$71.8433	$71.84	$71.85	$71.80
Purchase #6	$138.60	10.641%	$153.3484	$153.35	$153.35	$153.30
Purchase #7	$49.73	10.784%	$55.0929	$55.09	$55.10	$55.10
7 purchase totals =	$422.35		$462.4762	$462.47	$462.50	$462.40