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	$225.63	7.646%	$242.8817	$242.88	$242.90	$242.90
Purchase #2	$61.72	13.698%	$70.1744	$70.17	$70.15	$70.20
Purchase #3	$249.71	8.842%	$271.7894	$271.79	$271.80	$271.80
Purchase #4	$191.93	4.453%	$200.4766	$200.48	$200.50	$200.50
Purchase #5	$162.76	11.870%	$182.0796	$182.08	$182.10	$182.10
Purchase #6	$131.86	11.756%	$147.3615	$147.36	$147.35	$147.40
Purchase #7	$13.61	13.674%	$15.471	$15.47	$15.45	$15.50
7 purchase totals =	$1,037.22		$1,130.2342	$1,130.23	$1,130.25	$1,130.40