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	$147.69	8.253%	$159.8789	$159.88	$159.90	$159.90
Purchase #2	$67.27	6.806%	$71.8484	$71.85	$71.85	$71.80
Purchase #3	$31.52	12.254%	$35.3825	$35.38	$35.40	$35.40
Purchase #4	$125.40	6.455%	$133.4946	$133.49	$133.50	$133.50
Purchase #5	$77.35	5.784%	$81.8239	$81.82	$81.80	$81.80
Purchase #6	$109.54	13.466%	$124.2907	$124.29	$124.30	$124.30
Purchase #7	$212.25	12.200%	$238.1445	$238.14	$238.15	$238.10
7 purchase totals =	$771.02		$844.8635	$844.85	$844.90	$844.80