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	$168.85	6.402%	$179.6598	$179.66	$179.65	$179.70
Purchase #2	$45.38	11.131%	$50.4312	$50.43	$50.45	$50.40
Purchase #3	$82.50	5.218%	$86.8049	$86.80	$86.80	$86.80
Purchase #4	$247.57	6.786%	$264.3701	$264.37	$264.35	$264.40
Purchase #5	$179.72	11.619%	$200.6017	$200.60	$200.60	$200.60
Purchase #6	$115.82	4.283%	$120.7806	$120.78	$120.80	$120.80
Purchase #7	$175.58	6.170%	$186.4133	$186.41	$186.40	$186.40
7 purchase totals =	$1,015.42		$1,089.0616	$1,089.05	$1,089.05	$1,089.10