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	$249.31	4.642%	$260.883	$260.88	$260.90	$260.90
Purchase #2	$90.67	5.130%	$95.3214	$95.32	$95.30	$95.30
Purchase #3	$201.31	7.704%	$216.8189	$216.82	$216.80	$216.80
Purchase #4	$149.98	12.820%	$169.2074	$169.21	$169.20	$169.20
Purchase #5	$36.69	7.451%	$39.4238	$39.42	$39.40	$39.40
Purchase #6	$38.63	9.290%	$42.2187	$42.22	$42.20	$42.20
Purchase #7	$173.34	12.675%	$195.3108	$195.31	$195.30	$195.30
7 purchase totals =	$939.93		$1,019.1840	$1,019.18	$1,019.10	$1,019.10