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	$209.72	6.649%	$223.6643	$223.66	$223.65	$223.70
Purchase #2	$35.49	5.563%	$37.4643	$37.46	$37.45	$37.50
Purchase #3	$54.30	10.431%	$59.964	$59.96	$59.95	$60.00
Purchase #4	$239.77	13.836%	$272.9446	$272.94	$272.95	$272.90
Purchase #5	$89.32	13.519%	$101.3952	$101.40	$101.40	$101.40
Purchase #6	$104.25	9.410%	$114.0599	$114.06	$114.05	$114.10
Purchase #7	$184.94	4.344%	$192.9738	$192.97	$192.95	$193.00
7 purchase totals =	$917.79		$1,002.4661	$1,002.45	$1,002.40	$1,002.60