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	$47.31	12.244%	$53.1026	$53.10	$53.10	$53.10
Purchase #2	$238.64	8.715%	$259.4375	$259.44	$259.45	$259.40
Purchase #3	$215.62	3.199%	$222.5177	$222.52	$222.50	$222.50
Purchase #4	$48.51	13.180%	$54.9036	$54.90	$54.90	$54.90
Purchase #5	$169.35	3.551%	$175.3636	$175.36	$175.35	$175.40
Purchase #6	$225.40	5.558%	$237.9277	$237.93	$237.95	$237.90
Purchase #7	$165.80	7.558%	$178.3312	$178.33	$178.35	$178.30
7 purchase totals =	$1,110.63		$1,181.5839	$1,181.58	$1,181.60	$1,181.50