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	$81.65	6.226%	$86.7335	$86.73	$86.75	$86.70
Purchase #2	$36.92	3.213%	$38.1062	$38.11	$38.10	$38.10
Purchase #3	$87.45	13.794%	$99.5129	$99.51	$99.50	$99.50
Purchase #4	$160.38	11.680%	$179.1124	$179.11	$179.10	$179.10
Purchase #5	$41.64	12.488%	$46.84	$46.84	$46.85	$46.80
Purchase #6	$112.39	13.205%	$127.2311	$127.23	$127.25	$127.20
Purchase #7	$175.67	4.271%	$183.1729	$183.17	$183.15	$183.20
7 purchase totals =	$696.10		$760.7090	$760.70	$760.70	$760.60