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	$81.71	3.543%	$84.605	$84.61	$84.60	$84.60
Purchase #2	$101.32	10.814%	$112.2767	$112.28	$112.30	$112.30
Purchase #3	$100.69	12.566%	$113.3427	$113.34	$113.35	$113.30
Purchase #4	$221.65	10.654%	$245.2646	$245.26	$245.25	$245.30
Purchase #5	$113.85	11.603%	$127.06	$127.06	$127.05	$127.10
Purchase #6	$48.57	13.264%	$55.0123	$55.01	$55.00	$55.00
Purchase #7	$81.67	5.865%	$86.4599	$86.46	$86.45	$86.50
7 purchase totals =	$749.46		$824.0212	$824.02	$824.00	$824.10