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	$102.77	6.661%	$109.6155	$109.62	$109.60	$109.60
Purchase #2	$152.91	3.482%	$158.2343	$158.23	$158.25	$158.20
Purchase #3	$163.61	11.281%	$182.0668	$182.07	$182.05	$182.10
Purchase #4	$85.53	4.576%	$89.4439	$89.44	$89.45	$89.40
Purchase #5	$234.79	3.560%	$243.1485	$243.15	$243.15	$243.10
Purchase #6	$201.36	10.193%	$221.8846	$221.88	$221.90	$221.90
Purchase #7	$98.56	5.158%	$103.6437	$103.64	$103.65	$103.60
7 purchase totals =	$1,039.53		$1,108.0373	$1,108.03	$1,108.05	$1,107.90