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	$167.59	11.466%	$186.8059	$186.81	$186.80	$186.80
Purchase #2	$90.86	9.199%	$99.2182	$99.22	$99.20	$99.20
Purchase #3	$140.94	6.751%	$150.4549	$150.45	$150.45	$150.50
Purchase #4	$107.60	11.706%	$120.1957	$120.20	$120.20	$120.20
Purchase #5	$133.71	7.477%	$143.7075	$143.71	$143.70	$143.70
Purchase #6	$233.72	7.706%	$251.7305	$251.73	$251.75	$251.70
Purchase #7	$206.36	4.445%	$215.5327	$215.53	$215.55	$215.50
7 purchase totals =	$1,080.78		$1,167.6454	$1,167.65	$1,167.65	$1,167.60