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	$27.90	5.381%	$29.4013	$29.40	$29.40	$29.40
Purchase #2	$95.35	8.744%	$103.6874	$103.69	$103.70	$103.70
Purchase #3	$189.59	7.847%	$204.4671	$204.47	$204.45	$204.50
Purchase #4	$240.92	9.490%	$263.7833	$263.78	$263.80	$263.80
Purchase #5	$195.25	10.495%	$215.7415	$215.74	$215.75	$215.70
Purchase #6	$236.62	8.118%	$255.8288	$255.83	$255.85	$255.80
Purchase #7	$182.94	7.372%	$196.4263	$196.43	$196.45	$196.40
7 purchase totals =	$1,168.57		$1,269.3357	$1,269.34	$1,269.40	$1,269.30