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	$67.32	11.773%	$75.2456	$75.25	$75.25	$75.20
Purchase #2	$216.40	8.373%	$234.5192	$234.52	$234.50	$234.50
Purchase #3	$160.72	5.741%	$169.9469	$169.95	$169.95	$169.90
Purchase #4	$67.99	6.419%	$72.3543	$72.35	$72.35	$72.40
Purchase #5	$97.61	8.818%	$106.2172	$106.22	$106.20	$106.20
Purchase #6	$147.27	6.521%	$156.8735	$156.87	$156.85	$156.90
Purchase #7	$215.31	8.625%	$233.8805	$233.88	$233.90	$233.90
7 purchase totals =	$972.62		$1,049.0372	$1,049.04	$1,049.00	$1,049.00