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	$104.64	4.493%	$109.3415	$109.34	$109.35	$109.30
Purchase #2	$197.96	12.667%	$223.0356	$223.04	$223.05	$223.00
Purchase #3	$222.45	10.666%	$246.1765	$246.18	$246.20	$246.20
Purchase #4	$50.63	5.338%	$53.3326	$53.33	$53.35	$53.30
Purchase #5	$157.72	11.596%	$176.0092	$176.01	$176.00	$176.00
Purchase #6	$249.86	9.409%	$273.3693	$273.37	$273.35	$273.40
Purchase #7	$45.94	9.630%	$50.364	$50.36	$50.35	$50.40
7 purchase totals =	$1,029.20		$1,131.6287	$1,131.63	$1,131.65	$1,131.60