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	$216.44	3.262%	$223.5003	$223.50	$223.50	$223.50
Purchase #2	$40.27	12.257%	$45.2059	$45.21	$45.20	$45.20
Purchase #3	$163.47	8.240%	$176.9399	$176.94	$176.95	$176.90
Purchase #4	$156.26	6.376%	$166.2231	$166.22	$166.20	$166.20
Purchase #5	$127.71	4.416%	$133.3497	$133.35	$133.35	$133.30
Purchase #6	$80.90	12.791%	$91.2479	$91.25	$91.25	$91.20
Purchase #7	$244.53	12.524%	$275.1549	$275.15	$275.15	$275.20
7 purchase totals =	$1,029.58		$1,111.6217	$1,111.62	$1,111.60	$1,111.50