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	$19.91	3.828%	$20.6722	$20.67	$20.65	$20.70
Purchase #2	$70.92	4.109%	$73.8341	$73.83	$73.85	$73.80
Purchase #3	$159.31	6.556%	$169.7544	$169.75	$169.75	$169.80
Purchase #4	$217.33	4.166%	$226.384	$226.38	$226.40	$226.40
Purchase #5	$130.85	7.618%	$140.8182	$140.82	$140.80	$140.80
Purchase #6	$176.25	11.512%	$196.5399	$196.54	$196.55	$196.50
Purchase #7	$212.30	6.405%	$225.8978	$225.90	$225.90	$225.90
7 purchase totals =	$986.87		$1,053.9006	$1,053.89	$1,053.90	$1,053.90