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	$114.66	5.443%	$120.9009	$120.90	$120.90	$120.90
Purchase #2	$130.52	13.822%	$148.5605	$148.56	$148.55	$148.60
Purchase #3	$184.93	3.696%	$191.765	$191.77	$191.75	$191.80
Purchase #4	$186.43	13.523%	$211.6409	$211.64	$211.65	$211.60
Purchase #5	$124.45	4.380%	$129.9009	$129.90	$129.90	$129.90
Purchase #6	$231.37	5.688%	$244.5303	$244.53	$244.55	$244.50
Purchase #7	$140.33	3.730%	$145.5643	$145.56	$145.55	$145.60
7 purchase totals =	$1,112.69		$1,192.8628	$1,192.86	$1,192.85	$1,192.90