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	$240.65	11.267%	$267.764	$267.76	$267.75	$267.80
Purchase #2	$162.74	6.262%	$172.9308	$172.93	$172.95	$172.90
Purchase #3	$167.31	11.233%	$186.1039	$186.10	$186.10	$186.10
Purchase #4	$61.90	3.258%	$63.9167	$63.92	$63.90	$63.90
Purchase #5	$57.83	7.701%	$62.2835	$62.28	$62.30	$62.30
Purchase #6	$225.59	12.530%	$253.8564	$253.86	$253.85	$253.90
Purchase #7	$9.77	5.511%	$10.3084	$10.31	$10.30	$10.30
7 purchase totals =	$925.79		$1,017.1637	$1,017.16	$1,017.15	$1,017.20