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	$42.86	5.871%	$45.3763	$45.38	$45.40	$45.40
Purchase #2	$16.50	8.513%	$17.9046	$17.90	$17.90	$17.90
Purchase #3	$79.34	8.521%	$86.1006	$86.10	$86.10	$86.10
Purchase #4	$232.88	4.407%	$243.143	$243.14	$243.15	$243.10
Purchase #5	$237.59	12.488%	$267.2602	$267.26	$267.25	$267.30
Purchase #6	$188.59	4.179%	$196.4712	$196.47	$196.45	$196.50
Purchase #7	$24.90	9.119%	$27.1706	$27.17	$27.15	$27.20
7 purchase totals =	$822.66		$883.4265	$883.42	$883.40	$883.50