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	$145.74	3.416%	$150.7185	$150.72	$150.70	$150.70
Purchase #2	$167.29	8.411%	$181.3608	$181.36	$181.35	$181.40
Purchase #3	$100.85	10.274%	$111.2113	$111.21	$111.20	$111.20
Purchase #4	$100.40	8.620%	$109.0545	$109.05	$109.05	$109.10
Purchase #5	$238.35	10.228%	$262.7284	$262.73	$262.75	$262.70
Purchase #6	$86.67	5.745%	$91.6492	$91.65	$91.65	$91.60
Purchase #7	$248.83	6.436%	$264.8447	$264.84	$264.85	$264.80
7 purchase totals =	$1,088.13		$1,171.5674	$1,171.56	$1,171.55	$1,171.50