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	$54.59	3.127%	$56.297	$56.30	$56.30	$56.30
Purchase #2	$51.69	3.736%	$53.6211	$53.62	$53.60	$53.60
Purchase #3	$191.37	12.117%	$214.5583	$214.56	$214.55	$214.60
Purchase #4	$239.60	12.388%	$269.2816	$269.28	$269.30	$269.30
Purchase #5	$215.82	7.283%	$231.5382	$231.54	$231.55	$231.50
Purchase #6	$135.74	12.385%	$152.5514	$152.55	$152.55	$152.60
Purchase #7	$132.81	13.339%	$150.5255	$150.53	$150.55	$150.50
7 purchase totals =	$1,021.62		$1,128.3731	$1,128.38	$1,128.40	$1,128.40