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	$124.72	12.569%	$140.3961	$140.40	$140.40	$140.40
Purchase #2	$178.80	9.846%	$196.4046	$196.40	$196.40	$196.40
Purchase #3	$236.80	11.644%	$264.373	$264.37	$264.35	$264.40
Purchase #4	$147.76	11.305%	$164.4643	$164.46	$164.45	$164.50
Purchase #5	$35.46	9.581%	$38.8574	$38.86	$38.85	$38.90
Purchase #6	$127.59	8.479%	$138.4084	$138.41	$138.40	$138.40
Purchase #7	$211.85	10.316%	$233.7044	$233.70	$233.70	$233.70
7 purchase totals =	$1,062.98		$1,176.6082	$1,176.60	$1,176.55	$1,176.70