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	$86.31	3.653%	$89.4629	$89.46	$89.45	$89.50
Purchase #2	$182.61	3.252%	$188.5485	$188.55	$188.55	$188.50
Purchase #3	$126.30	5.518%	$133.2692	$133.27	$133.25	$133.30
Purchase #4	$207.58	8.497%	$225.2181	$225.22	$225.20	$225.20
Purchase #5	$79.71	12.418%	$89.6084	$89.61	$89.60	$89.60
Purchase #6	$95.33	3.765%	$98.9192	$98.92	$98.90	$98.90
Purchase #7	$243.96	7.729%	$262.8157	$262.82	$262.80	$262.80
7 purchase totals =	$1,021.80		$1,087.8420	$1,087.85	$1,087.75	$1,087.80