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	$98.38	13.356%	$111.5196	$111.52	$111.50	$111.50
Purchase #2	$16.36	3.395%	$16.9154	$16.92	$16.90	$16.90
Purchase #3	$153.59	7.650%	$165.3396	$165.34	$165.35	$165.30
Purchase #4	$125.58	12.488%	$141.2624	$141.26	$141.25	$141.30
Purchase #5	$114.67	9.406%	$125.4559	$125.46	$125.45	$125.50
Purchase #6	$178.55	6.783%	$190.661	$190.66	$190.65	$190.70
Purchase #7	$86.72	11.456%	$96.6546	$96.65	$96.65	$96.70
7 purchase totals =	$773.85		$847.8085	$847.81	$847.75	$847.90