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	$250.94	3.281%	$259.1733	$259.17	$259.15	$259.20
Purchase #2	$26.58	4.333%	$27.7317	$27.73	$27.75	$27.70
Purchase #3	$67.56	6.607%	$72.0237	$72.02	$72.00	$72.00
Purchase #4	$202.60	13.312%	$229.5701	$229.57	$229.55	$229.60
Purchase #5	$162.83	9.868%	$178.8981	$178.90	$178.90	$178.90
Purchase #6	$148.63	11.258%	$165.3628	$165.36	$165.35	$165.40
Purchase #7	$132.47	7.358%	$142.2171	$142.22	$142.20	$142.20
7 purchase totals =	$991.61		$1,074.9768	$1,074.97	$1,074.90	$1,075.00