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	$161.41	11.417%	$179.8382	$179.84	$179.85	$179.80
Purchase #2	$29.64	13.417%	$33.6168	$33.62	$33.60	$33.60
Purchase #3	$110.80	11.774%	$123.8456	$123.85	$123.85	$123.80
Purchase #4	$6.93	11.782%	$7.7465	$7.75	$7.75	$7.70
Purchase #5	$96.39	3.349%	$99.6181	$99.62	$99.60	$99.60
Purchase #6	$41.82	8.203%	$45.2505	$45.25	$45.25	$45.30
Purchase #7	$81.28	5.167%	$85.4797	$85.48	$85.50	$85.50
7 purchase totals =	$528.27		$575.3954	$575.41	$575.40	$575.30