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	$203.89	5.835%	$215.787	$215.79	$215.80	$215.80
Purchase #2	$176.53	5.536%	$186.3027	$186.30	$186.30	$186.30
Purchase #3	$67.56	6.315%	$71.8264	$71.83	$71.85	$71.80
Purchase #4	$64.34	12.635%	$72.4694	$72.47	$72.45	$72.50
Purchase #5	$204.28	10.205%	$225.1268	$225.13	$225.15	$225.10
Purchase #6	$178.45	3.640%	$184.9456	$184.95	$184.95	$184.90
Purchase #7	$53.71	6.795%	$57.3596	$57.36	$57.35	$57.40
7 purchase totals =	$948.76		$1,013.8175	$1,013.83	$1,013.85	$1,013.80