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	$171.65	10.677%	$189.9771	$189.98	$190.00	$190.00
Purchase #2	$104.97	6.732%	$112.0366	$112.04	$112.05	$112.00
Purchase #3	$183.88	9.802%	$201.9039	$201.90	$201.90	$201.90
Purchase #4	$55.92	6.407%	$59.5028	$59.50	$59.50	$59.50
Purchase #5	$79.59	13.848%	$90.6116	$90.61	$90.60	$90.60
Purchase #6	$199.62	8.489%	$216.5657	$216.57	$216.55	$216.60
Purchase #7	$214.76	3.400%	$222.0618	$222.06	$222.05	$222.10
7 purchase totals =	$1,010.39		$1,092.6595	$1,092.66	$1,092.65	$1,092.70