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	$44.43	10.576%	$49.1289	$49.13	$49.15	$49.10
Purchase #2	$151.62	4.343%	$158.2049	$158.20	$158.20	$158.20
Purchase #3	$209.54	6.802%	$223.7929	$223.79	$223.80	$223.80
Purchase #4	$131.81	8.471%	$142.9756	$142.98	$143.00	$143.00
Purchase #5	$243.57	8.726%	$264.8239	$264.82	$264.80	$264.80
Purchase #6	$114.85	10.771%	$127.2205	$127.22	$127.20	$127.20
Purchase #7	$65.28	3.731%	$67.7156	$67.72	$67.70	$67.70
7 purchase totals =	$961.10		$1,033.8623	$1,033.86	$1,033.85	$1,033.80