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	$142.43	3.230%	$147.0305	$147.03	$147.05	$147.00
Purchase #2	$82.26	8.280%	$89.0711	$89.07	$89.05	$89.10
Purchase #3	$219.97	10.854%	$243.8455	$243.85	$243.85	$243.80
Purchase #4	$72.91	12.748%	$82.2046	$82.20	$82.20	$82.20
Purchase #5	$174.38	12.498%	$196.174	$196.17	$196.15	$196.20
Purchase #6	$182.54	9.827%	$200.4782	$200.48	$200.50	$200.50
Purchase #7	$181.50	9.135%	$198.08	$198.08	$198.10	$198.10
7 purchase totals =	$1,055.99		$1,156.8839	$1,156.88	$1,156.90	$1,156.90