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	$161.95	4.574%	$169.3576	$169.36	$169.35	$169.40
Purchase #2	$36.64	4.585%	$38.3199	$38.32	$38.30	$38.30
Purchase #3	$204.62	12.839%	$230.8912	$230.89	$230.90	$230.90
Purchase #4	$80.96	10.213%	$89.2284	$89.23	$89.25	$89.20
Purchase #5	$181.31	3.317%	$187.3241	$187.32	$187.30	$187.30
Purchase #6	$189.61	10.874%	$210.2282	$210.23	$210.25	$210.20
Purchase #7	$97.81	8.647%	$106.2676	$106.27	$106.25	$106.30
7 purchase totals =	$952.90		$1,031.6170	$1,031.62	$1,031.60	$1,031.60