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	$226.30	12.627%	$254.8749	$254.87	$254.85	$254.90
Purchase #2	$96.48	8.831%	$105.0001	$105.00	$105.00	$105.00
Purchase #3	$55.38	11.798%	$61.9137	$61.91	$61.90	$61.90
Purchase #4	$116.74	3.209%	$120.4862	$120.49	$120.50	$120.50
Purchase #5	$233.25	11.808%	$260.7922	$260.79	$260.80	$260.80
Purchase #6	$179.84	9.282%	$196.5327	$196.53	$196.55	$196.50
Purchase #7	$80.88	9.849%	$88.8459	$88.85	$88.85	$88.80
7 purchase totals =	$988.87		$1,088.4457	$1,088.44	$1,088.45	$1,088.40