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	$189.88	5.697%	$200.6975	$200.70	$200.70	$200.70
Purchase #2	$165.89	13.322%	$187.9899	$187.99	$188.00	$188.00
Purchase #3	$153.46	13.825%	$174.6758	$174.68	$174.70	$174.70
Purchase #4	$229.75	6.686%	$245.1111	$245.11	$245.10	$245.10
Purchase #5	$50.70	6.720%	$54.107	$54.11	$54.10	$54.10
Purchase #6	$80.39	11.359%	$89.5215	$89.52	$89.50	$89.50
Purchase #7	$131.39	4.723%	$137.5955	$137.60	$137.60	$137.60
7 purchase totals =	$1,001.46		$1,089.6983	$1,089.71	$1,089.70	$1,089.70