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	$102.75	8.521%	$111.5053	$111.51	$111.50	$111.50
Purchase #2	$28.97	3.159%	$29.8852	$29.89	$29.90	$29.90
Purchase #3	$182.88	6.808%	$195.3305	$195.33	$195.35	$195.30
Purchase #4	$250.89	6.577%	$267.391	$267.39	$267.40	$267.40
Purchase #5	$172.55	7.104%	$184.808	$184.81	$184.80	$184.80
Purchase #6	$209.91	8.258%	$227.2444	$227.24	$227.25	$227.20
Purchase #7	$145.97	13.189%	$165.222	$165.22	$165.20	$165.20
7 purchase totals =	$1,093.92		$1,181.3864	$1,181.39	$1,181.40	$1,181.30