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	$63.76	13.141%	$72.1387	$72.14	$72.15	$72.10
Purchase #2	$248.85	7.230%	$266.8419	$266.84	$266.85	$266.80
Purchase #3	$179.63	6.511%	$191.3257	$191.33	$191.35	$191.30
Purchase #4	$224.26	13.753%	$255.1025	$255.10	$255.10	$255.10
Purchase #5	$45.47	9.843%	$49.9456	$49.95	$49.95	$49.90
Purchase #6	$26.37	4.668%	$27.601	$27.60	$27.60	$27.60
Purchase #7	$25.44	13.500%	$28.8744	$28.87	$28.85	$28.90
7 purchase totals =	$813.78		$891.8298	$891.83	$891.85	$891.70