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	$97.71	13.658%	$111.0552	$111.06	$111.05	$111.10
Purchase #2	$82.46	7.593%	$88.7212	$88.72	$88.70	$88.70
Purchase #3	$76.86	3.309%	$79.4033	$79.40	$79.40	$79.40
Purchase #4	$158.77	10.214%	$174.9868	$174.99	$175.00	$175.00
Purchase #5	$89.82	3.511%	$92.9736	$92.97	$92.95	$93.00
Purchase #6	$13.44	13.609%	$15.269	$15.27	$15.25	$15.30
Purchase #7	$97.90	13.831%	$111.4405	$111.44	$111.45	$111.40
7 purchase totals =	$616.96		$673.8496	$673.85	$673.80	$673.90