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	$198.76	13.651%	$225.8927	$225.89	$225.90	$225.90
Purchase #2	$109.84	13.780%	$124.976	$124.98	$125.00	$125.00
Purchase #3	$127.45	11.443%	$142.0341	$142.03	$142.05	$142.00
Purchase #4	$215.73	8.394%	$233.8384	$233.84	$233.85	$233.80
Purchase #5	$96.44	9.519%	$105.6201	$105.62	$105.60	$105.60
Purchase #6	$228.98	5.372%	$241.2808	$241.28	$241.30	$241.30
Purchase #7	$196.52	6.573%	$209.4373	$209.44	$209.45	$209.40
7 purchase totals =	$1,173.72		$1,283.0794	$1,283.08	$1,283.15	$1,283.00