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	$229.49	13.837%	$261.2445	$261.24	$261.25	$261.20
Purchase #2	$7.35	10.148%	$8.0959	$8.10	$8.10	$8.10
Purchase #3	$24.56	10.688%	$27.185	$27.19	$27.20	$27.20
Purchase #4	$82.41	4.280%	$85.9371	$85.94	$85.95	$85.90
Purchase #5	$102.70	8.762%	$111.6986	$111.70	$111.70	$111.70
Purchase #6	$109.76	12.331%	$123.2945	$123.29	$123.30	$123.30
Purchase #7	$70.69	13.872%	$80.4961	$80.50	$80.50	$80.50
7 purchase totals =	$626.96		$697.9517	$697.96	$698.00	$697.90