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	$156.62	9.610%	$171.6712	$171.67	$171.65	$171.70
Purchase #2	$46.98	13.458%	$53.3026	$53.30	$53.30	$53.30
Purchase #3	$69.81	12.645%	$78.6375	$78.64	$78.65	$78.60
Purchase #4	$25.86	12.546%	$29.1044	$29.10	$29.10	$29.10
Purchase #5	$199.55	11.679%	$222.8554	$222.86	$222.85	$222.90
Purchase #6	$183.88	12.245%	$206.3961	$206.40	$206.40	$206.40
Purchase #7	$167.48	7.677%	$180.3374	$180.34	$180.35	$180.30
7 purchase totals =	$850.18		$942.3046	$942.31	$942.30	$942.30