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	$123.87	4.651%	$129.6312	$129.63	$129.65	$129.60
Purchase #2	$27.88	11.637%	$31.1244	$31.12	$31.10	$31.10
Purchase #3	$46.31	12.604%	$52.1469	$52.15	$52.15	$52.10
Purchase #4	$29.98	11.728%	$33.4961	$33.50	$33.50	$33.50
Purchase #5	$177.43	7.354%	$190.4782	$190.48	$190.50	$190.50
Purchase #6	$170.36	7.155%	$182.5493	$182.55	$182.55	$182.50
Purchase #7	$78.64	3.787%	$81.6181	$81.62	$81.60	$81.60
7 purchase totals =	$654.47		$701.0442	$701.05	$701.05	$700.90