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	$151.61	11.807%	$169.5106	$169.51	$169.50	$169.50
Purchase #2	$146.66	9.628%	$160.7804	$160.78	$160.80	$160.80
Purchase #3	$98.47	9.525%	$107.8493	$107.85	$107.85	$107.80
Purchase #4	$6.62	10.244%	$7.2982	$7.30	$7.30	$7.30
Purchase #5	$163.38	3.227%	$168.6523	$168.65	$168.65	$168.70
Purchase #6	$183.64	4.287%	$191.5126	$191.51	$191.50	$191.50
Purchase #7	$237.28	11.646%	$264.9136	$264.91	$264.90	$264.90
7 purchase totals =	$987.66		$1,070.5170	$1,070.51	$1,070.50	$1,070.50