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	$89.52	11.849%	$100.1272	$100.13	$100.15	$100.10
Purchase #2	$174.56	11.151%	$194.0252	$194.03	$194.05	$194.00
Purchase #3	$39.65	10.401%	$43.774	$43.77	$43.75	$43.80
Purchase #4	$89.67	8.427%	$97.2265	$97.23	$97.25	$97.20
Purchase #5	$195.87	4.391%	$204.4707	$204.47	$204.45	$204.50
Purchase #6	$151.70	3.317%	$156.7319	$156.73	$156.75	$156.70
Purchase #7	$231.59	4.432%	$241.8541	$241.85	$241.85	$241.90
7 purchase totals =	$972.56		$1,038.2096	$1,038.21	$1,038.25	$1,038.20