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	$86.80	4.595%	$90.7885	$90.79	$90.80	$90.80
Purchase #2	$211.33	5.561%	$223.0821	$223.08	$223.10	$223.10
Purchase #3	$212.61	7.563%	$228.6897	$228.69	$228.70	$228.70
Purchase #4	$68.26	13.298%	$77.3372	$77.34	$77.35	$77.30
Purchase #5	$124.52	3.505%	$128.8844	$128.88	$128.90	$128.90
Purchase #6	$38.84	4.637%	$40.641	$40.64	$40.65	$40.60
Purchase #7	$150.82	9.104%	$164.5507	$164.55	$164.55	$164.60
7 purchase totals =	$893.18		$953.9736	$953.97	$954.05	$954.00