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	$145.76	3.790%	$151.2843	$151.28	$151.30	$151.30
Purchase #2	$6.59	7.621%	$7.0922	$7.09	$7.10	$7.10
Purchase #3	$36.81	11.221%	$40.9405	$40.94	$40.95	$40.90
Purchase #4	$209.45	4.519%	$218.915	$218.92	$218.90	$218.90
Purchase #5	$247.50	9.234%	$270.3542	$270.35	$270.35	$270.40
Purchase #6	$39.55	13.869%	$45.0352	$45.04	$45.05	$45.00
Purchase #7	$104.46	10.688%	$115.6247	$115.62	$115.60	$115.60
7 purchase totals =	$790.12		$849.2461	$849.24	$849.25	$849.20