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	$174.36	6.434%	$185.5783	$185.58	$185.60	$185.60
Purchase #2	$98.77	4.662%	$103.3747	$103.37	$103.35	$103.40
Purchase #3	$150.52	4.610%	$157.459	$157.46	$157.45	$157.50
Purchase #4	$174.75	6.372%	$185.8851	$185.89	$185.90	$185.90
Purchase #5	$127.72	5.296%	$134.4841	$134.48	$134.50	$134.50
Purchase #6	$233.69	13.310%	$264.7941	$264.79	$264.80	$264.80
Purchase #7	$248.96	12.353%	$279.714	$279.71	$279.70	$279.70
7 purchase totals =	$1,208.77		$1,311.2893	$1,311.28	$1,311.30	$1,311.40