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	$100.64	7.358%	$108.0451	$108.05	$108.05	$108.00
Purchase #2	$119.48	10.298%	$131.7841	$131.78	$131.80	$131.80
Purchase #3	$19.59	10.113%	$21.5711	$21.57	$21.55	$21.60
Purchase #4	$113.48	5.815%	$120.0789	$120.08	$120.10	$120.10
Purchase #5	$145.28	11.570%	$162.0889	$162.09	$162.10	$162.10
Purchase #6	$188.35	11.567%	$210.1364	$210.14	$210.15	$210.10
Purchase #7	$105.40	12.205%	$118.2641	$118.26	$118.25	$118.30
7 purchase totals =	$792.22		$871.9686	$871.97	$872.00	$872.00