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	$123.62	3.870%	$128.4041	$128.40	$128.40	$128.40
Purchase #2	$160.25	4.449%	$167.3795	$167.38	$167.40	$167.40
Purchase #3	$188.46	5.512%	$198.8479	$198.85	$198.85	$198.80
Purchase #4	$227.75	12.855%	$257.0273	$257.03	$257.05	$257.00
Purchase #5	$111.27	3.465%	$115.1255	$115.13	$115.15	$115.10
Purchase #6	$59.64	3.301%	$61.6087	$61.61	$61.60	$61.60
Purchase #7	$77.47	12.851%	$87.4257	$87.43	$87.45	$87.40
7 purchase totals =	$948.46		$1,015.8187	$1,015.83	$1,015.90	$1,015.70