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	$62.38	11.762%	$69.7171	$69.72	$69.70	$69.70
Purchase #2	$191.27	4.524%	$199.9231	$199.92	$199.90	$199.90
Purchase #3	$14.73	4.383%	$15.3756	$15.38	$15.40	$15.40
Purchase #4	$248.33	10.380%	$274.1067	$274.11	$274.10	$274.10
Purchase #5	$92.76	12.444%	$104.3031	$104.30	$104.30	$104.30
Purchase #6	$93.94	5.669%	$99.2655	$99.27	$99.25	$99.30
Purchase #7	$72.96	12.802%	$82.3003	$82.30	$82.30	$82.30
7 purchase totals =	$776.37		$844.9914	$845.00	$844.95	$845.00