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	$112.88	5.592%	$119.1922	$119.19	$119.20	$119.20
Purchase #2	$240.46	6.437%	$255.9384	$255.94	$255.95	$255.90
Purchase #3	$127.34	5.406%	$134.224	$134.22	$134.20	$134.20
Purchase #4	$103.92	13.290%	$117.731	$117.73	$117.75	$117.70
Purchase #5	$79.29	13.227%	$89.7777	$89.78	$89.80	$89.80
Purchase #6	$87.56	12.505%	$98.5094	$98.51	$98.50	$98.50
Purchase #7	$51.84	11.568%	$57.8369	$57.84	$57.85	$57.80
7 purchase totals =	$803.29		$873.2096	$873.21	$873.25	$873.10