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	$138.58	10.293%	$152.844	$152.84	$152.85	$152.80
Purchase #2	$136.53	10.479%	$150.837	$150.84	$150.85	$150.80
Purchase #3	$152.91	6.640%	$163.0632	$163.06	$163.05	$163.10
Purchase #4	$86.78	11.325%	$96.6078	$96.61	$96.60	$96.60
Purchase #5	$210.90	5.539%	$222.5818	$222.58	$222.60	$222.60
Purchase #6	$39.28	8.709%	$42.7009	$42.70	$42.70	$42.70
Purchase #7	$100.89	5.599%	$106.5388	$106.54	$106.55	$106.50
7 purchase totals =	$865.87		$935.1735	$935.17	$935.20	$935.10