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	$173.36	9.672%	$190.1274	$190.13	$190.15	$190.10
Purchase #2	$120.55	4.864%	$126.4136	$126.41	$126.40	$126.40
Purchase #3	$5.69	3.220%	$5.8732	$5.87	$5.85	$5.90
Purchase #4	$225.73	10.801%	$250.1111	$250.11	$250.10	$250.10
Purchase #5	$64.48	4.707%	$67.5151	$67.52	$67.50	$67.50
Purchase #6	$54.86	7.849%	$59.166	$59.17	$59.15	$59.20
Purchase #7	$35.69	6.558%	$38.0306	$38.03	$38.05	$38.00
7 purchase totals =	$680.36		$737.2370	$737.24	$737.20	$737.20