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	$217.73	10.860%	$241.3755	$241.38	$241.40	$241.40
Purchase #2	$159.59	6.117%	$169.3521	$169.35	$169.35	$169.40
Purchase #3	$100.66	6.459%	$107.1616	$107.16	$107.15	$107.20
Purchase #4	$230.28	12.229%	$258.4409	$258.44	$258.45	$258.40
Purchase #5	$6.80	10.507%	$7.5145	$7.51	$7.50	$7.50
Purchase #6	$237.61	11.804%	$265.6575	$265.66	$265.65	$265.70
Purchase #7	$25.89	11.655%	$28.9075	$28.91	$28.90	$28.90
7 purchase totals =	$978.56		$1,078.4096	$1,078.41	$1,078.40	$1,078.50