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	$250.53	7.109%	$268.3402	$268.34	$268.35	$268.30
Purchase #2	$129.79	9.185%	$141.7112	$141.71	$141.70	$141.70
Purchase #3	$69.73	3.673%	$72.2912	$72.29	$72.30	$72.30
Purchase #4	$200.31	5.354%	$211.0346	$211.03	$211.05	$211.00
Purchase #5	$234.84	9.384%	$256.8774	$256.88	$256.90	$256.90
Purchase #6	$45.77	12.689%	$51.5778	$51.58	$51.60	$51.60
Purchase #7	$36.67	8.818%	$39.9036	$39.90	$39.90	$39.90
7 purchase totals =	$967.64		$1,041.7360	$1,041.73	$1,041.80	$1,041.70