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	$38.72	5.564%	$40.8744	$40.87	$40.85	$40.90
Purchase #2	$243.54	7.642%	$262.1513	$262.15	$262.15	$262.20
Purchase #3	$28.65	8.740%	$31.154	$31.15	$31.15	$31.20
Purchase #4	$23.79	3.373%	$24.5924	$24.59	$24.60	$24.60
Purchase #5	$195.25	5.144%	$205.2937	$205.29	$205.30	$205.30
Purchase #6	$248.86	13.221%	$281.7618	$281.76	$281.75	$281.80
Purchase #7	$184.74	5.789%	$195.4346	$195.43	$195.45	$195.40
7 purchase totals =	$963.55		$1,041.2622	$1,041.24	$1,041.25	$1,041.40