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	$115.80	10.339%	$127.7726	$127.77	$127.75	$127.80
Purchase #2	$179.35	12.274%	$201.3634	$201.36	$201.35	$201.40
Purchase #3	$61.77	3.386%	$63.8615	$63.86	$63.85	$63.90
Purchase #4	$109.79	4.115%	$114.3079	$114.31	$114.30	$114.30
Purchase #5	$36.75	8.432%	$39.8488	$39.85	$39.85	$39.80
Purchase #6	$157.81	9.488%	$172.783	$172.78	$172.80	$172.80
Purchase #7	$81.95	10.475%	$90.5343	$90.53	$90.55	$90.50
7 purchase totals =	$743.22		$810.4715	$810.46	$810.45	$810.50