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	$23.49	11.310%	$26.1467	$26.15	$26.15	$26.10
Purchase #2	$91.81	9.254%	$100.3061	$100.31	$100.30	$100.30
Purchase #3	$138.82	12.318%	$155.9198	$155.92	$155.90	$155.90
Purchase #4	$84.72	7.840%	$91.362	$91.36	$91.35	$91.40
Purchase #5	$178.57	4.292%	$186.2342	$186.23	$186.25	$186.20
Purchase #6	$70.47	11.243%	$78.3929	$78.39	$78.40	$78.40
Purchase #7	$79.27	9.423%	$86.7396	$86.74	$86.75	$86.70
7 purchase totals =	$667.15		$725.1013	$725.10	$725.10	$725.00