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	$187.94	5.545%	$198.3613	$198.36	$198.35	$198.40
Purchase #2	$197.32	10.371%	$217.7841	$217.78	$217.80	$217.80
Purchase #3	$100.82	8.427%	$109.3161	$109.32	$109.30	$109.30
Purchase #4	$215.35	3.412%	$222.6977	$222.70	$222.70	$222.70
Purchase #5	$61.27	9.455%	$67.0631	$67.06	$67.05	$67.10
Purchase #6	$149.28	3.761%	$154.8944	$154.89	$154.90	$154.90
Purchase #7	$38.31	7.450%	$41.1641	$41.16	$41.15	$41.20
7 purchase totals =	$950.29		$1,011.2808	$1,011.27	$1,011.25	$1,011.40