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	$171.30	9.386%	$187.3782	$187.38	$187.40	$187.40
Purchase #2	$213.74	13.455%	$242.4987	$242.50	$242.50	$242.50
Purchase #3	$90.92	11.326%	$101.2176	$101.22	$101.20	$101.20
Purchase #4	$72.45	11.672%	$80.9064	$80.91	$80.90	$80.90
Purchase #5	$199.38	11.484%	$222.2768	$222.28	$222.30	$222.30
Purchase #6	$243.71	3.385%	$251.9596	$251.96	$251.95	$252.00
Purchase #7	$98.95	11.391%	$110.2214	$110.22	$110.20	$110.20
7 purchase totals =	$1,090.45		$1,196.4587	$1,196.47	$1,196.45	$1,196.50