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	$184.78	6.427%	$196.6558	$196.66	$196.65	$196.70
Purchase #2	$72.82	11.478%	$81.1783	$81.18	$81.20	$81.20
Purchase #3	$62.77	10.788%	$69.5416	$69.54	$69.55	$69.50
Purchase #4	$111.41	7.831%	$120.1345	$120.13	$120.15	$120.10
Purchase #5	$157.43	8.837%	$171.3421	$171.34	$171.35	$171.30
Purchase #6	$20.34	7.478%	$21.861	$21.86	$21.85	$21.90
Purchase #7	$167.98	4.220%	$175.0688	$175.07	$175.05	$175.10
7 purchase totals =	$777.53		$835.7821	$835.78	$835.80	$835.80