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	$112.26	6.856%	$119.9565	$119.96	$119.95	$120.00
Purchase #2	$63.63	12.686%	$71.7021	$71.70	$71.70	$71.70
Purchase #3	$207.70	6.856%	$221.9399	$221.94	$221.95	$221.90
Purchase #4	$219.89	8.489%	$238.5565	$238.56	$238.55	$238.60
Purchase #5	$99.46	4.664%	$104.0988	$104.10	$104.10	$104.10
Purchase #6	$66.55	5.355%	$70.1138	$70.11	$70.10	$70.10
Purchase #7	$208.25	12.780%	$234.8644	$234.86	$234.85	$234.90
7 purchase totals =	$977.74		$1,061.2320	$1,061.23	$1,061.20	$1,061.30