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	$136.66	11.256%	$152.0424	$152.04	$152.05	$152.00
Purchase #2	$26.97	4.722%	$28.2435	$28.24	$28.25	$28.20
Purchase #3	$249.50	5.786%	$263.9361	$263.94	$263.95	$263.90
Purchase #4	$115.60	11.640%	$129.0558	$129.06	$129.05	$129.10
Purchase #5	$65.90	7.511%	$70.8497	$70.85	$70.85	$70.80
Purchase #6	$60.50	11.158%	$67.2506	$67.25	$67.25	$67.30
Purchase #7	$62.82	13.698%	$71.4251	$71.43	$71.45	$71.40
7 purchase totals =	$717.95		$782.8032	$782.81	$782.85	$782.70