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	$89.85	13.413%	$101.9016	$101.90	$101.90	$101.90
Purchase #2	$159.62	9.546%	$174.8573	$174.86	$174.85	$174.90
Purchase #3	$210.59	11.263%	$234.3088	$234.31	$234.30	$234.30
Purchase #4	$177.91	10.181%	$196.023	$196.02	$196.00	$196.00
Purchase #5	$139.30	8.714%	$151.4386	$151.44	$151.45	$151.40
Purchase #6	$184.25	8.537%	$199.9794	$199.98	$200.00	$200.00
Purchase #7	$181.99	9.253%	$198.8295	$198.83	$198.85	$198.80
7 purchase totals =	$1,143.51		$1,257.3382	$1,257.34	$1,257.35	$1,257.30