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	$67.76	5.572%	$71.5356	$71.54	$71.55	$71.50
Purchase #2	$95.33	3.855%	$99.005	$99.01	$99.00	$99.00
Purchase #3	$13.61	3.689%	$14.1121	$14.11	$14.10	$14.10
Purchase #4	$27.92	13.869%	$31.7922	$31.79	$31.80	$31.80
Purchase #5	$84.49	6.299%	$89.812	$89.81	$89.80	$89.80
Purchase #6	$61.40	10.285%	$67.715	$67.72	$67.70	$67.70
Purchase #7	$109.53	5.125%	$115.1434	$115.14	$115.15	$115.10
7 purchase totals =	$460.04		$489.1153	$489.12	$489.10	$489.00