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	$151.28	9.537%	$165.7076	$165.71	$165.70	$165.70
Purchase #2	$204.98	3.165%	$211.4676	$211.47	$211.45	$211.50
Purchase #3	$28.46	11.609%	$31.7639	$31.76	$31.75	$31.80
Purchase #4	$17.36	9.801%	$19.0615	$19.06	$19.05	$19.10
Purchase #5	$202.50	9.687%	$222.1162	$222.12	$222.10	$222.10
Purchase #6	$140.87	12.264%	$158.1463	$158.15	$158.15	$158.10
Purchase #7	$115.92	6.598%	$123.5684	$123.57	$123.55	$123.60
7 purchase totals =	$861.37		$931.8315	$931.84	$931.75	$931.90