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	$208.45	8.156%	$225.4512	$225.45	$225.45	$225.50
Purchase #2	$105.27	8.713%	$114.4422	$114.44	$114.45	$114.40
Purchase #3	$118.26	6.223%	$125.6193	$125.62	$125.60	$125.60
Purchase #4	$225.73	5.757%	$238.7253	$238.73	$238.75	$238.70
Purchase #5	$115.81	6.274%	$123.0759	$123.08	$123.10	$123.10
Purchase #6	$79.74	12.360%	$89.5959	$89.60	$89.60	$89.60
Purchase #7	$222.87	8.740%	$242.3488	$242.35	$242.35	$242.30
7 purchase totals =	$1,076.13		$1,159.2586	$1,159.27	$1,159.30	$1,159.20