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	$237.72	12.850%	$268.267	$268.27	$268.25	$268.30
Purchase #2	$180.25	4.424%	$188.2243	$188.22	$188.20	$188.20
Purchase #3	$68.92	5.383%	$72.63	$72.63	$72.65	$72.60
Purchase #4	$121.91	4.356%	$127.2204	$127.22	$127.20	$127.20
Purchase #5	$203.93	5.484%	$215.1135	$215.11	$215.10	$215.10
Purchase #6	$13.31	9.752%	$14.608	$14.61	$14.60	$14.60
Purchase #7	$228.75	5.430%	$241.1711	$241.17	$241.15	$241.20
7 purchase totals =	$1,054.79		$1,127.2343	$1,127.23	$1,127.15	$1,127.20