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	$146.46	5.140%	$153.988	$153.99	$154.00	$154.00
Purchase #2	$62.97	12.779%	$71.0169	$71.02	$71.00	$71.00
Purchase #3	$6.87	7.304%	$7.3718	$7.37	$7.35	$7.40
Purchase #4	$12.33	13.109%	$13.9463	$13.95	$13.95	$13.90
Purchase #5	$117.86	4.702%	$123.4018	$123.40	$123.40	$123.40
Purchase #6	$72.31	13.393%	$81.9945	$81.99	$82.00	$82.00
Purchase #7	$119.84	9.783%	$131.5639	$131.56	$131.55	$131.60
7 purchase totals =	$538.64		$583.2832	$583.28	$583.25	$583.30