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	$49.81	3.592%	$51.5992	$51.60	$51.60	$51.60
Purchase #2	$149.55	11.671%	$167.004	$167.00	$167.00	$167.00
Purchase #3	$242.59	9.199%	$264.9059	$264.91	$264.90	$264.90
Purchase #4	$163.30	10.844%	$181.0083	$181.01	$181.00	$181.00
Purchase #5	$137.27	5.138%	$144.3229	$144.32	$144.30	$144.30
Purchase #6	$109.25	6.231%	$116.0574	$116.06	$116.05	$116.10
Purchase #7	$110.28	7.502%	$118.5532	$118.55	$118.55	$118.60
7 purchase totals =	$962.05		$1,043.4509	$1,043.45	$1,043.40	$1,043.50