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	$210.36	6.315%	$223.6442	$223.64	$223.65	$223.60
Purchase #2	$170.44	4.419%	$177.9717	$177.97	$177.95	$178.00
Purchase #3	$233.65	11.695%	$260.9754	$260.98	$261.00	$261.00
Purchase #4	$86.71	9.407%	$94.8668	$94.87	$94.85	$94.90
Purchase #5	$65.86	8.525%	$71.4746	$71.47	$71.45	$71.50
Purchase #6	$80.86	10.436%	$89.2985	$89.30	$89.30	$89.30
Purchase #7	$156.85	7.374%	$168.4161	$168.42	$168.40	$168.40
7 purchase totals =	$1,004.73		$1,086.6473	$1,086.65	$1,086.60	$1,086.70