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	$167.84	6.844%	$179.327	$179.33	$179.35	$179.30
Purchase #2	$150.38	10.514%	$166.191	$166.19	$166.20	$166.20
Purchase #3	$152.42	5.299%	$160.4967	$160.50	$160.50	$160.50
Purchase #4	$115.28	5.256%	$121.3391	$121.34	$121.35	$121.30
Purchase #5	$179.51	11.129%	$199.4877	$199.49	$199.50	$199.50
Purchase #6	$122.45	7.122%	$131.1709	$131.17	$131.15	$131.20
Purchase #7	$118.38	7.460%	$127.2111	$127.21	$127.20	$127.20
7 purchase totals =	$1,006.26		$1,085.2235	$1,085.23	$1,085.25	$1,085.20