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	$124.58	10.207%	$137.2959	$137.30	$137.30	$137.30
Purchase #2	$104.69	4.361%	$109.2555	$109.26	$109.25	$109.30
Purchase #3	$15.95	6.112%	$16.9249	$16.92	$16.90	$16.90
Purchase #4	$88.50	3.845%	$91.9028	$91.90	$91.90	$91.90
Purchase #5	$37.52	4.695%	$39.2816	$39.28	$39.30	$39.30
Purchase #6	$222.74	11.827%	$249.0835	$249.08	$249.10	$249.10
Purchase #7	$76.73	11.590%	$85.623	$85.62	$85.60	$85.60
7 purchase totals =	$670.71		$729.3672	$729.36	$729.35	$729.40