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	$132.78	7.498%	$142.7358	$142.74	$142.75	$142.70
Purchase #2	$48.28	7.575%	$51.9372	$51.94	$51.95	$51.90
Purchase #3	$97.30	10.124%	$107.1507	$107.15	$107.15	$107.20
Purchase #4	$67.57	6.770%	$72.1445	$72.14	$72.15	$72.10
Purchase #5	$92.62	5.322%	$97.5492	$97.55	$97.55	$97.50
Purchase #6	$137.39	4.462%	$143.5203	$143.52	$143.50	$143.50
Purchase #7	$83.84	6.252%	$89.0817	$89.08	$89.10	$89.10
7 purchase totals =	$659.78		$704.1194	$704.12	$704.15	$704.00