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	$16.61	7.691%	$17.8875	$17.89	$17.90	$17.90
Purchase #2	$195.40	3.368%	$201.9811	$201.98	$202.00	$202.00
Purchase #3	$98.77	6.198%	$104.8918	$104.89	$104.90	$104.90
Purchase #4	$17.45	4.647%	$18.2609	$18.26	$18.25	$18.30
Purchase #5	$39.59	4.234%	$41.2662	$41.27	$41.25	$41.30
Purchase #6	$54.70	9.564%	$59.9315	$59.93	$59.95	$59.90
Purchase #7	$19.46	7.109%	$20.8434	$20.84	$20.85	$20.80
7 purchase totals =	$441.98		$465.0624	$465.06	$465.10	$465.10