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	$148.34	4.155%	$154.5035	$154.50	$154.50	$154.50
Purchase #2	$38.27	4.772%	$40.0962	$40.10	$40.10	$40.10
Purchase #3	$119.36	3.751%	$123.8372	$123.84	$123.85	$123.80
Purchase #4	$89.40	10.288%	$98.5975	$98.60	$98.60	$98.60
Purchase #5	$51.75	4.624%	$54.1429	$54.14	$54.15	$54.10
Purchase #6	$110.58	6.489%	$117.7555	$117.76	$117.75	$117.80
Purchase #7	$131.92	8.576%	$143.2335	$143.23	$143.25	$143.20
7 purchase totals =	$689.62		$732.1663	$732.17	$732.20	$732.10