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	$49.57	13.482%	$56.253	$56.25	$56.25	$56.30
Purchase #2	$241.30	8.731%	$262.3679	$262.37	$262.35	$262.40
Purchase #3	$128.28	3.375%	$132.6095	$132.61	$132.60	$132.60
Purchase #4	$85.30	8.697%	$92.7185	$92.72	$92.70	$92.70
Purchase #5	$165.73	8.242%	$179.3895	$179.39	$179.40	$179.40
Purchase #6	$84.69	12.289%	$95.0976	$95.10	$95.10	$95.10
Purchase #7	$171.48	6.567%	$182.7411	$182.74	$182.75	$182.70
7 purchase totals =	$926.35		$1,001.1771	$1,001.18	$1,001.15	$1,001.20