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	$113.51	10.208%	$125.0971	$125.10	$125.10	$125.10
Purchase #2	$150.65	11.519%	$168.0034	$168.00	$168.00	$168.00
Purchase #3	$81.32	12.350%	$91.363	$91.36	$91.35	$91.40
Purchase #4	$73.28	6.592%	$78.1106	$78.11	$78.10	$78.10
Purchase #5	$76.39	3.179%	$78.8184	$78.82	$78.80	$78.80
Purchase #6	$135.38	13.824%	$154.0949	$154.09	$154.10	$154.10
Purchase #7	$27.62	3.597%	$28.6135	$28.61	$28.60	$28.60
7 purchase totals =	$658.15		$724.1009	$724.09	$724.05	$724.10