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	$108.60	3.650%	$112.5639	$112.56	$112.55	$112.60
Purchase #2	$245.41	4.245%	$255.8277	$255.83	$255.85	$255.80
Purchase #3	$228.50	9.481%	$250.1641	$250.16	$250.15	$250.20
Purchase #4	$34.78	3.148%	$35.8749	$35.87	$35.85	$35.90
Purchase #5	$238.95	11.436%	$266.2763	$266.28	$266.30	$266.30
Purchase #6	$20.75	6.818%	$22.1647	$22.16	$22.15	$22.20
Purchase #7	$97.98	5.690%	$103.5551	$103.56	$103.55	$103.60
7 purchase totals =	$974.97		$1,046.4267	$1,046.42	$1,046.40	$1,046.60