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	$92.34	9.560%	$101.1677	$101.17	$101.15	$101.20
Purchase #2	$185.89	11.683%	$207.6075	$207.61	$207.60	$207.60
Purchase #3	$123.55	3.519%	$127.8977	$127.90	$127.90	$127.90
Purchase #4	$48.67	13.791%	$55.3821	$55.38	$55.40	$55.40
Purchase #5	$79.54	7.675%	$85.6447	$85.64	$85.65	$85.60
Purchase #6	$84.58	8.294%	$91.5951	$91.60	$91.60	$91.60
Purchase #7	$103.35	11.733%	$115.4761	$115.48	$115.50	$115.50
7 purchase totals =	$717.92		$784.7709	$784.78	$784.80	$784.80