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	$214.68	8.580%	$233.0995	$233.10	$233.10	$233.10
Purchase #2	$190.44	8.265%	$206.1799	$206.18	$206.20	$206.20
Purchase #3	$123.54	3.215%	$127.5118	$127.51	$127.50	$127.50
Purchase #4	$175.70	13.271%	$199.0171	$199.02	$199.00	$199.00
Purchase #5	$72.62	10.698%	$80.3889	$80.39	$80.40	$80.40
Purchase #6	$55.87	10.163%	$61.5481	$61.55	$61.55	$61.50
Purchase #7	$132.90	7.398%	$142.7319	$142.73	$142.75	$142.70
7 purchase totals =	$965.75		$1,050.4772	$1,050.48	$1,050.50	$1,050.40