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	$222.99	9.112%	$243.3088	$243.31	$243.30	$243.30
Purchase #2	$111.29	5.315%	$117.2051	$117.21	$117.20	$117.20
Purchase #3	$31.49	3.349%	$32.5446	$32.54	$32.55	$32.50
Purchase #4	$98.28	11.727%	$109.8053	$109.81	$109.80	$109.80
Purchase #5	$151.25	11.641%	$168.857	$168.86	$168.85	$168.90
Purchase #6	$168.72	13.408%	$191.342	$191.34	$191.35	$191.30
Purchase #7	$176.81	8.737%	$192.2579	$192.26	$192.25	$192.30
7 purchase totals =	$960.83		$1,055.3207	$1,055.33	$1,055.30	$1,055.30