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	$65.31	11.617%	$72.8971	$72.90	$72.90	$72.90
Purchase #2	$232.74	7.430%	$250.0326	$250.03	$250.05	$250.00
Purchase #3	$239.37	3.155%	$246.9221	$246.92	$246.90	$246.90
Purchase #4	$130.79	10.787%	$144.8983	$144.90	$144.90	$144.90
Purchase #5	$182.31	3.294%	$188.3153	$188.32	$188.30	$188.30
Purchase #6	$145.81	3.822%	$151.3829	$151.38	$151.40	$151.40
Purchase #7	$200.63	6.580%	$213.8315	$213.83	$213.85	$213.80
7 purchase totals =	$1,196.96		$1,268.2798	$1,268.28	$1,268.30	$1,268.20