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	$211.80	5.708%	$223.8895	$223.89	$223.90	$223.90
Purchase #2	$158.94	6.835%	$169.8035	$169.80	$169.80	$169.80
Purchase #3	$48.76	9.713%	$53.4961	$53.50	$53.50	$53.50
Purchase #4	$130.56	8.385%	$141.5075	$141.51	$141.50	$141.50
Purchase #5	$152.80	11.152%	$169.8403	$169.84	$169.85	$169.80
Purchase #6	$24.51	8.642%	$26.6282	$26.63	$26.65	$26.60
Purchase #7	$242.68	5.432%	$255.8624	$255.86	$255.85	$255.90
7 purchase totals =	$970.05		$1,041.0275	$1,041.03	$1,041.05	$1,041.00