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	$116.37	12.558%	$130.9837	$130.98	$131.00	$131.00
Purchase #2	$52.86	3.840%	$54.8898	$54.89	$54.90	$54.90
Purchase #3	$64.46	11.424%	$71.8239	$71.82	$71.80	$71.80
Purchase #4	$62.80	12.526%	$70.6663	$70.67	$70.65	$70.70
Purchase #5	$242.83	6.766%	$259.2599	$259.26	$259.25	$259.30
Purchase #6	$226.31	3.592%	$234.4391	$234.44	$234.45	$234.40
Purchase #7	$128.35	11.145%	$142.6546	$142.65	$142.65	$142.70
7 purchase totals =	$893.98		$964.7173	$964.71	$964.70	$964.80