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	$43.42	4.364%	$45.3148	$45.31	$45.30	$45.30
Purchase #2	$103.25	12.226%	$115.8733	$115.87	$115.85	$115.90
Purchase #3	$198.87	7.220%	$213.2284	$213.23	$213.25	$213.20
Purchase #4	$162.33	5.214%	$170.7939	$170.79	$170.80	$170.80
Purchase #5	$189.55	4.570%	$198.2124	$198.21	$198.20	$198.20
Purchase #6	$65.27	11.503%	$72.778	$72.78	$72.80	$72.80
Purchase #7	$188.40	10.860%	$208.8602	$208.86	$208.85	$208.90
7 purchase totals =	$951.09		$1,025.0610	$1,025.05	$1,025.05	$1,025.10