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	$186.64	5.431%	$196.7764	$196.78	$196.80	$196.80
Purchase #2	$109.69	6.351%	$116.6564	$116.66	$116.65	$116.70
Purchase #3	$96.81	6.739%	$103.334	$103.33	$103.35	$103.30
Purchase #4	$67.59	9.515%	$74.0212	$74.02	$74.00	$74.00
Purchase #5	$148.78	4.411%	$155.3427	$155.34	$155.35	$155.30
Purchase #6	$102.91	6.711%	$109.8163	$109.82	$109.80	$109.80
Purchase #7	$113.77	11.783%	$127.1755	$127.18	$127.20	$127.20
7 purchase totals =	$826.19		$883.1225	$883.13	$883.15	$883.10