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	$190.84	4.113%	$198.6892	$198.69	$198.70	$198.70
Purchase #2	$199.34	13.509%	$226.2688	$226.27	$226.25	$226.30
Purchase #3	$185.38	13.710%	$210.7956	$210.80	$210.80	$210.80
Purchase #4	$16.97	11.395%	$18.9037	$18.90	$18.90	$18.90
Purchase #5	$90.38	8.689%	$98.2331	$98.23	$98.25	$98.20
Purchase #6	$248.65	6.522%	$264.867	$264.87	$264.85	$264.90
Purchase #7	$41.66	3.858%	$43.2672	$43.27	$43.25	$43.30
7 purchase totals =	$973.22		$1,061.0246	$1,061.03	$1,061.00	$1,061.10