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	$185.50	8.260%	$200.8223	$200.82	$200.80	$200.80
Purchase #2	$187.89	6.787%	$200.6421	$200.64	$200.65	$200.60
Purchase #3	$97.66	13.314%	$110.6625	$110.66	$110.65	$110.70
Purchase #4	$35.97	12.603%	$40.5033	$40.50	$40.50	$40.50
Purchase #5	$64.86	12.170%	$72.7535	$72.75	$72.75	$72.80
Purchase #6	$101.94	7.531%	$109.6171	$109.62	$109.60	$109.60
Purchase #7	$73.29	4.195%	$76.3645	$76.36	$76.35	$76.40
7 purchase totals =	$747.11		$811.3653	$811.35	$811.30	$811.40