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	$44.90	6.417%	$47.7812	$47.78	$47.80	$47.80
Purchase #2	$191.47	12.187%	$214.8044	$214.80	$214.80	$214.80
Purchase #3	$53.65	10.205%	$59.125	$59.13	$59.15	$59.10
Purchase #4	$143.59	7.530%	$154.4023	$154.40	$154.40	$154.40
Purchase #5	$222.58	3.807%	$231.0536	$231.05	$231.05	$231.10
Purchase #6	$38.74	11.354%	$43.1385	$43.14	$43.15	$43.10
Purchase #7	$94.61	3.628%	$98.0425	$98.04	$98.05	$98.00
7 purchase totals =	$789.54		$848.3475	$848.34	$848.40	$848.30