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	$56.52	8.356%	$61.2428	$61.24	$61.25	$61.20
Purchase #2	$168.55	8.566%	$182.988	$182.99	$183.00	$183.00
Purchase #3	$205.55	10.854%	$227.8604	$227.86	$227.85	$227.90
Purchase #4	$118.70	7.218%	$127.2678	$127.27	$127.25	$127.30
Purchase #5	$98.41	11.240%	$109.4713	$109.47	$109.45	$109.50
Purchase #6	$37.91	5.354%	$39.9397	$39.94	$39.95	$39.90
Purchase #7	$242.52	9.817%	$266.3282	$266.33	$266.35	$266.30
7 purchase totals =	$928.16		$1,015.0982	$1,015.10	$1,015.10	$1,015.10