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	$62.91	4.799%	$65.9291	$65.93	$65.95	$65.90
Purchase #2	$151.27	4.322%	$157.8079	$157.81	$157.80	$157.80
Purchase #3	$198.32	7.426%	$213.0472	$213.05	$213.05	$213.00
Purchase #4	$190.74	3.147%	$196.7426	$196.74	$196.75	$196.70
Purchase #5	$56.82	5.286%	$59.8235	$59.82	$59.80	$59.80
Purchase #6	$8.63	3.218%	$8.9077	$8.91	$8.90	$8.90
Purchase #7	$80.80	11.558%	$90.1389	$90.14	$90.15	$90.10
7 purchase totals =	$749.49		$792.3969	$792.40	$792.40	$792.20