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	$164.83	8.319%	$178.5422	$178.54	$178.55	$178.50
Purchase #2	$214.56	6.434%	$228.3648	$228.36	$228.35	$228.40
Purchase #3	$100.77	8.337%	$109.1712	$109.17	$109.15	$109.20
Purchase #4	$64.83	9.729%	$71.1373	$71.14	$71.15	$71.10
Purchase #5	$213.77	3.341%	$220.9121	$220.91	$220.90	$220.90
Purchase #6	$182.48	9.356%	$199.5528	$199.55	$199.55	$199.60
Purchase #7	$151.42	12.820%	$170.832	$170.83	$170.85	$170.80
7 purchase totals =	$1,092.66		$1,178.5124	$1,178.50	$1,178.50	$1,178.50