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	$188.89	5.296%	$198.8936	$198.89	$198.90	$198.90
Purchase #2	$118.89	7.516%	$127.8258	$127.83	$127.85	$127.80
Purchase #3	$76.52	11.484%	$85.3076	$85.31	$85.30	$85.30
Purchase #4	$159.97	4.622%	$167.3638	$167.36	$167.35	$167.40
Purchase #5	$150.51	10.485%	$166.291	$166.29	$166.30	$166.30
Purchase #6	$66.58	4.250%	$69.4097	$69.41	$69.40	$69.40
Purchase #7	$191.42	8.304%	$207.3155	$207.32	$207.30	$207.30
7 purchase totals =	$952.78		$1,022.4070	$1,022.41	$1,022.40	$1,022.40