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	$37.89	10.418%	$41.8374	$41.84	$41.85	$41.80
Purchase #2	$167.84	8.344%	$181.8446	$181.84	$181.85	$181.80
Purchase #3	$64.91	13.817%	$73.8786	$73.88	$73.90	$73.90
Purchase #4	$144.76	3.869%	$150.3608	$150.36	$150.35	$150.40
Purchase #5	$72.50	7.442%	$77.8955	$77.90	$77.90	$77.90
Purchase #6	$38.36	13.324%	$43.4711	$43.47	$43.45	$43.50
Purchase #7	$166.93	7.855%	$180.0424	$180.04	$180.05	$180.00
7 purchase totals =	$693.19		$749.3304	$749.33	$749.35	$749.30