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	$116.28	9.606%	$127.4499	$127.45	$127.45	$127.40
Purchase #2	$168.51	12.472%	$189.5266	$189.53	$189.55	$189.50
Purchase #3	$65.79	9.550%	$72.0729	$72.07	$72.05	$72.10
Purchase #4	$123.93	3.199%	$127.8945	$127.89	$127.90	$127.90
Purchase #5	$105.42	12.283%	$118.3687	$118.37	$118.35	$118.40
Purchase #6	$17.73	7.819%	$19.1163	$19.12	$19.10	$19.10
Purchase #7	$102.79	7.383%	$110.379	$110.38	$110.40	$110.40
7 purchase totals =	$700.45		$764.8079	$764.81	$764.80	$764.80