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	$89.27	11.209%	$99.2763	$99.28	$99.30	$99.30
Purchase #2	$63.39	6.689%	$67.6302	$67.63	$67.65	$67.60
Purchase #3	$182.65	7.580%	$196.4949	$196.49	$196.50	$196.50
Purchase #4	$97.61	3.361%	$100.8907	$100.89	$100.90	$100.90
Purchase #5	$130.78	13.415%	$148.3241	$148.32	$148.30	$148.30
Purchase #6	$29.33	7.820%	$31.6236	$31.62	$31.60	$31.60
Purchase #7	$195.61	6.214%	$207.7652	$207.77	$207.75	$207.80
7 purchase totals =	$788.64		$852.0050	$852.00	$852.00	$852.00