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	$172.86	7.676%	$186.1287	$186.13	$186.15	$186.10
Purchase #2	$201.87	3.757%	$209.4543	$209.45	$209.45	$209.50
Purchase #3	$181.34	7.829%	$195.5371	$195.54	$195.55	$195.50
Purchase #4	$92.99	8.149%	$100.5678	$100.57	$100.55	$100.60
Purchase #5	$43.80	3.646%	$45.3969	$45.40	$45.40	$45.40
Purchase #6	$179.94	9.707%	$197.4068	$197.41	$197.40	$197.40
Purchase #7	$75.25	3.680%	$78.0192	$78.02	$78.00	$78.00
7 purchase totals =	$948.05		$1,012.5108	$1,012.52	$1,012.50	$1,012.50