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	$218.82	3.829%	$227.1986	$227.20	$227.20	$227.20
Purchase #2	$130.89	10.706%	$144.9031	$144.90	$144.90	$144.90
Purchase #3	$207.72	3.831%	$215.6778	$215.68	$215.70	$215.70
Purchase #4	$137.33	3.465%	$142.0885	$142.09	$142.10	$142.10
Purchase #5	$97.52	5.164%	$102.5559	$102.56	$102.55	$102.60
Purchase #6	$67.40	6.185%	$71.5687	$71.57	$71.55	$71.60
Purchase #7	$110.61	4.659%	$115.7633	$115.76	$115.75	$115.80
7 purchase totals =	$970.29		$1,019.7559	$1,019.76	$1,019.75	$1,019.90