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	$14.92	4.845%	$15.6429	$15.64	$15.65	$15.60
Purchase #2	$42.40	7.563%	$45.6067	$45.61	$45.60	$45.60
Purchase #3	$58.41	5.417%	$61.5741	$61.57	$61.55	$61.60
Purchase #4	$20.49	11.803%	$22.9084	$22.91	$22.90	$22.90
Purchase #5	$160.83	12.767%	$181.3632	$181.36	$181.35	$181.40
Purchase #6	$88.78	13.845%	$101.0716	$101.07	$101.05	$101.10
Purchase #7	$73.61	7.279%	$78.9681	$78.97	$78.95	$79.00
7 purchase totals =	$459.44		$507.1350	$507.13	$507.05	$507.20