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	$95.99	5.427%	$101.1994	$101.20	$101.20	$101.20
Purchase #2	$219.64	9.868%	$241.3141	$241.31	$241.30	$241.30
Purchase #3	$181.33	7.310%	$194.5852	$194.59	$194.60	$194.60
Purchase #4	$44.85	11.626%	$50.0643	$50.06	$50.05	$50.10
Purchase #5	$60.82	6.409%	$64.718	$64.72	$64.70	$64.70
Purchase #6	$53.88	10.677%	$59.6328	$59.63	$59.65	$59.60
Purchase #7	$86.31	10.545%	$95.4114	$95.41	$95.40	$95.40
7 purchase totals =	$742.82		$806.9252	$806.92	$806.90	$806.90