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	$178.46	10.324%	$196.8842	$196.88	$196.90	$196.90
Purchase #2	$162.90	10.488%	$179.985	$179.99	$180.00	$180.00
Purchase #3	$13.31	11.742%	$14.8729	$14.87	$14.85	$14.90
Purchase #4	$231.31	8.753%	$251.5566	$251.56	$251.55	$251.60
Purchase #5	$180.32	6.371%	$191.8082	$191.81	$191.80	$191.80
Purchase #6	$92.59	12.814%	$104.4545	$104.45	$104.45	$104.50
Purchase #7	$47.27	9.492%	$51.7569	$51.76	$51.75	$51.80
7 purchase totals =	$906.16		$991.3183	$991.32	$991.30	$991.50