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	$41.98	4.430%	$43.8397	$43.84	$43.85	$43.80
Purchase #2	$211.76	6.479%	$225.4799	$225.48	$225.50	$225.50
Purchase #3	$41.33	3.636%	$42.8328	$42.83	$42.85	$42.80
Purchase #4	$244.55	8.579%	$265.5299	$265.53	$265.55	$265.50
Purchase #5	$147.96	11.512%	$164.9932	$164.99	$165.00	$165.00
Purchase #6	$24.55	13.213%	$27.7938	$27.79	$27.80	$27.80
Purchase #7	$243.73	10.736%	$269.8969	$269.90	$269.90	$269.90
7 purchase totals =	$955.86		$1,040.3662	$1,040.36	$1,040.45	$1,040.30