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	$216.28	12.162%	$242.584	$242.58	$242.60	$242.60
Purchase #2	$170.47	12.175%	$191.2247	$191.22	$191.20	$191.20
Purchase #3	$114.57	3.752%	$118.8687	$118.87	$118.85	$118.90
Purchase #4	$110.48	6.671%	$117.8501	$117.85	$117.85	$117.90
Purchase #5	$67.71	10.417%	$74.7634	$74.76	$74.75	$74.80
Purchase #6	$86.41	3.424%	$89.3687	$89.37	$89.35	$89.40
Purchase #7	$237.65	9.320%	$259.799	$259.80	$259.80	$259.80
7 purchase totals =	$1,003.57		$1,094.4586	$1,094.45	$1,094.40	$1,094.60