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	$59.61	3.350%	$61.6069	$61.61	$61.60	$61.60
Purchase #2	$145.37	11.629%	$162.2751	$162.28	$162.30	$162.30
Purchase #3	$240.66	7.714%	$259.2245	$259.22	$259.20	$259.20
Purchase #4	$234.32	10.668%	$259.3173	$259.32	$259.30	$259.30
Purchase #5	$60.40	6.593%	$64.3822	$64.38	$64.40	$64.40
Purchase #6	$181.76	4.741%	$190.3772	$190.38	$190.40	$190.40
Purchase #7	$99.51	13.152%	$112.5976	$112.60	$112.60	$112.60
7 purchase totals =	$1,021.63		$1,109.7808	$1,109.79	$1,109.80	$1,109.80