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	$211.86	8.455%	$229.7728	$229.77	$229.75	$229.80
Purchase #2	$20.96	5.320%	$22.0751	$22.08	$22.10	$22.10
Purchase #3	$192.85	13.757%	$219.3804	$219.38	$219.40	$219.40
Purchase #4	$112.89	13.223%	$127.8174	$127.82	$127.80	$127.80
Purchase #5	$141.46	12.872%	$159.6687	$159.67	$159.65	$159.70
Purchase #6	$173.93	5.872%	$184.1432	$184.14	$184.15	$184.10
Purchase #7	$89.53	9.704%	$98.218	$98.22	$98.20	$98.20
7 purchase totals =	$943.48		$1,041.0756	$1,041.08	$1,041.05	$1,041.10