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	$238.55	5.170%	$250.883	$250.88	$250.90	$250.90
Purchase #2	$248.81	4.208%	$259.2799	$259.28	$259.30	$259.30
Purchase #3	$102.39	6.670%	$109.2194	$109.22	$109.20	$109.20
Purchase #4	$84.71	5.847%	$89.663	$89.66	$89.65	$89.70
Purchase #5	$207.56	4.810%	$217.5436	$217.54	$217.55	$217.50
Purchase #6	$64.82	12.366%	$72.8356	$72.84	$72.85	$72.80
Purchase #7	$104.62	5.458%	$110.3302	$110.33	$110.35	$110.30
7 purchase totals =	$1,051.46		$1,109.7547	$1,109.75	$1,109.80	$1,109.70