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	$166.83	11.464%	$185.9554	$185.96	$185.95	$186.00
Purchase #2	$43.58	6.247%	$46.3024	$46.30	$46.30	$46.30
Purchase #3	$34.40	5.256%	$36.2081	$36.21	$36.20	$36.20
Purchase #4	$92.44	7.164%	$99.0624	$99.06	$99.05	$99.10
Purchase #5	$222.80	6.849%	$238.0596	$238.06	$238.05	$238.10
Purchase #6	$179.75	5.158%	$189.0215	$189.02	$189.00	$189.00
Purchase #7	$198.98	4.480%	$207.8943	$207.89	$207.90	$207.90
7 purchase totals =	$938.78		$1,002.5037	$1,002.50	$1,002.45	$1,002.60