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	$245.79	10.164%	$270.7721	$270.77	$270.75	$270.80
Purchase #2	$99.39	11.871%	$111.1886	$111.19	$111.20	$111.20
Purchase #3	$152.62	10.289%	$168.3231	$168.32	$168.30	$168.30
Purchase #4	$142.35	3.195%	$146.8981	$146.90	$146.90	$146.90
Purchase #5	$107.39	8.537%	$116.5579	$116.56	$116.55	$116.60
Purchase #6	$128.71	5.257%	$135.4763	$135.48	$135.50	$135.50
Purchase #7	$71.31	7.579%	$76.7146	$76.71	$76.70	$76.70
7 purchase totals =	$947.56		$1,025.9307	$1,025.93	$1,025.90	$1,026.00