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	$86.76	5.156%	$91.2333	$91.23	$91.25	$91.20
Purchase #2	$40.67	9.327%	$44.4633	$44.46	$44.45	$44.50
Purchase #3	$170.64	11.551%	$190.3506	$190.35	$190.35	$190.40
Purchase #4	$152.50	12.582%	$171.6876	$171.69	$171.70	$171.70
Purchase #5	$205.74	7.635%	$221.4482	$221.45	$221.45	$221.40
Purchase #6	$160.66	12.693%	$181.0526	$181.05	$181.05	$181.10
Purchase #7	$96.99	4.792%	$101.6378	$101.64	$101.65	$101.60
7 purchase totals =	$913.96		$1,001.8734	$1,001.87	$1,001.90	$1,001.90