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	$187.89	4.787%	$196.8843	$196.88	$196.90	$196.90
Purchase #2	$52.36	11.256%	$58.2536	$58.25	$58.25	$58.30
Purchase #3	$123.28	10.749%	$136.5314	$136.53	$136.55	$136.50
Purchase #4	$106.58	6.840%	$113.8701	$113.87	$113.85	$113.90
Purchase #5	$239.95	13.333%	$271.9425	$271.94	$271.95	$271.90
Purchase #6	$97.33	6.614%	$103.7674	$103.77	$103.75	$103.80
Purchase #7	$178.66	11.340%	$198.92	$198.92	$198.90	$198.90
7 purchase totals =	$986.05		$1,080.1693	$1,080.16	$1,080.15	$1,080.20