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	$215.57	7.186%	$231.0609	$231.06	$231.05	$231.10
Purchase #2	$81.56	6.545%	$86.8981	$86.90	$86.90	$86.90
Purchase #3	$162.71	4.682%	$170.3281	$170.33	$170.35	$170.30
Purchase #4	$130.62	7.868%	$140.8972	$140.90	$140.90	$140.90
Purchase #5	$78.33	3.705%	$81.2321	$81.23	$81.25	$81.20
Purchase #6	$227.72	13.578%	$258.6398	$258.64	$258.65	$258.60
Purchase #7	$115.93	6.377%	$123.3229	$123.32	$123.30	$123.30
7 purchase totals =	$1,012.44		$1,092.3791	$1,092.38	$1,092.40	$1,092.30