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	$56.55	8.562%	$61.3918	$61.39	$61.40	$61.40
Purchase #2	$57.59	13.844%	$65.5628	$65.56	$65.55	$65.60
Purchase #3	$146.37	6.799%	$156.3217	$156.32	$156.30	$156.30
Purchase #4	$115.56	8.850%	$125.7871	$125.79	$125.80	$125.80
Purchase #5	$99.33	4.646%	$103.9449	$103.94	$103.95	$103.90
Purchase #6	$123.71	5.161%	$130.0947	$130.09	$130.10	$130.10
Purchase #7	$98.30	10.671%	$108.7896	$108.79	$108.80	$108.80
7 purchase totals =	$697.41		$751.8926	$751.88	$751.90	$751.90