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	$202.57	10.183%	$223.1977	$223.20	$223.20	$223.20
Purchase #2	$219.56	9.229%	$239.8232	$239.82	$239.80	$239.80
Purchase #3	$117.41	8.400%	$127.2724	$127.27	$127.25	$127.30
Purchase #4	$169.32	10.265%	$186.7007	$186.70	$186.70	$186.70
Purchase #5	$99.52	10.277%	$109.7477	$109.75	$109.75	$109.70
Purchase #6	$70.65	8.612%	$76.7344	$76.73	$76.75	$76.70
Purchase #7	$125.77	13.168%	$142.3314	$142.33	$142.35	$142.30
7 purchase totals =	$1,004.80		$1,105.8075	$1,105.80	$1,105.80	$1,105.70