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	$149.98	3.220%	$154.8094	$154.81	$154.80	$154.80
Purchase #2	$55.25	8.166%	$59.7617	$59.76	$59.75	$59.80
Purchase #3	$210.49	13.217%	$238.3105	$238.31	$238.30	$238.30
Purchase #4	$174.89	11.531%	$195.0566	$195.06	$195.05	$195.10
Purchase #5	$179.38	6.849%	$191.6657	$191.67	$191.65	$191.70
Purchase #6	$149.33	12.852%	$168.5219	$168.52	$168.50	$168.50
Purchase #7	$165.98	12.434%	$186.618	$186.62	$186.60	$186.60
7 purchase totals =	$1,085.30		$1,194.7438	$1,194.75	$1,194.65	$1,194.80