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	$95.30	6.737%	$101.7204	$101.72	$101.70	$101.70
Purchase #2	$79.73	12.153%	$89.4196	$89.42	$89.40	$89.40
Purchase #3	$236.55	11.471%	$263.6847	$263.68	$263.70	$263.70
Purchase #4	$13.89	10.473%	$15.3447	$15.34	$15.35	$15.30
Purchase #5	$229.69	5.113%	$241.434	$241.43	$241.45	$241.40
Purchase #6	$156.27	9.451%	$171.0391	$171.04	$171.05	$171.00
Purchase #7	$123.96	3.551%	$128.3618	$128.36	$128.35	$128.40
7 purchase totals =	$935.39		$1,011.0043	$1,010.99	$1,011.00	$1,010.90