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	$213.33	7.841%	$230.0572	$230.06	$230.05	$230.10
Purchase #2	$236.72	11.687%	$264.3855	$264.39	$264.40	$264.40
Purchase #3	$136.39	12.371%	$153.2628	$153.26	$153.25	$153.30
Purchase #4	$18.32	9.460%	$20.0531	$20.05	$20.05	$20.10
Purchase #5	$13.85	12.564%	$15.5901	$15.59	$15.60	$15.60
Purchase #6	$56.56	8.212%	$61.2047	$61.20	$61.20	$61.20
Purchase #7	$24.90	11.443%	$27.7493	$27.75	$27.75	$27.70
7 purchase totals =	$700.07		$772.3027	$772.30	$772.30	$772.40