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	$74.83	11.789%	$83.6517	$83.65	$83.65	$83.70
Purchase #2	$198.95	12.257%	$223.3353	$223.34	$223.35	$223.30
Purchase #3	$163.94	13.869%	$186.6768	$186.68	$186.70	$186.70
Purchase #4	$218.50	12.349%	$245.4826	$245.48	$245.50	$245.50
Purchase #5	$90.96	10.336%	$100.3616	$100.36	$100.35	$100.40
Purchase #6	$146.59	6.734%	$156.4614	$156.46	$156.45	$156.50
Purchase #7	$193.39	7.700%	$208.281	$208.28	$208.30	$208.30
7 purchase totals =	$1,087.16		$1,204.2504	$1,204.25	$1,204.30	$1,204.40