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	$148.64	6.126%	$157.7457	$157.75	$157.75	$157.70
Purchase #2	$171.43	11.414%	$190.997	$191.00	$191.00	$191.00
Purchase #3	$131.52	5.760%	$139.0956	$139.10	$139.10	$139.10
Purchase #4	$78.92	8.437%	$85.5785	$85.58	$85.60	$85.60
Purchase #5	$121.90	5.314%	$128.3778	$128.38	$128.40	$128.40
Purchase #6	$190.46	11.651%	$212.6505	$212.65	$212.65	$212.70
Purchase #7	$212.74	7.431%	$228.5487	$228.55	$228.55	$228.50
7 purchase totals =	$1,055.61		$1,142.9938	$1,143.01	$1,143.05	$1,143.00