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	$164.93	11.361%	$183.6677	$183.67	$183.65	$183.70
Purchase #2	$173.25	7.435%	$186.1311	$186.13	$186.15	$186.10
Purchase #3	$164.83	12.136%	$184.8338	$184.83	$184.85	$184.80
Purchase #4	$50.89	5.127%	$53.4991	$53.50	$53.50	$53.50
Purchase #5	$91.72	11.367%	$102.1458	$102.15	$102.15	$102.10
Purchase #6	$153.67	8.752%	$167.1192	$167.12	$167.10	$167.10
Purchase #7	$89.34	5.568%	$94.3145	$94.31	$94.30	$94.30
7 purchase totals =	$888.63		$971.7112	$971.71	$971.70	$971.60