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	$185.91	3.833%	$193.0359	$193.04	$193.05	$193.00
Purchase #2	$110.83	4.799%	$116.1487	$116.15	$116.15	$116.10
Purchase #3	$78.55	10.474%	$86.7773	$86.78	$86.80	$86.80
Purchase #4	$12.25	3.760%	$12.7106	$12.71	$12.70	$12.70
Purchase #5	$29.71	9.685%	$32.5874	$32.59	$32.60	$32.60
Purchase #6	$193.75	3.553%	$200.6339	$200.63	$200.65	$200.60
Purchase #7	$224.30	9.180%	$244.8907	$244.89	$244.90	$244.90
7 purchase totals =	$835.30		$886.7845	$886.79	$886.85	$886.70